"Sandra Bullock is not a party to this litigation," James' attorney, Marilyn Slifman, said in a statement to People magazine Friday. "Mr. James's sole concern is for the safety, welfare and best interests of his daughter. The proper forum to resolve this case is in the courtroom."
Slifman called Lindemulder's claims, made on "Good Morning America" earlier this week, "inaccurate and unfortunate."
"It hurts tremendously, the accusations, especially from Sandra," Lindemulder said on "GMA" Wednesday in her first interview about the case. "Even more so because we've never sat down and talked. You know, that's the one thing that I wish more than anything, for a remedy for what's happening here, is just communication."
Bullock, the perpetual girl-next-door actress famous for films including "The Proposal" and "Miss Congeniality," has been helping her husband raise his 5-year-old daughter, Sunny, since January, when Lindemulder was in prison for tax evasion.
Now out of jail, Lindemulder faces a fierce custody battle against James, the biker and star of cable TV's "Monster Garage," and his megawatt Hollywood actress wife who has said she relishes her role as a stepmother.
"What would give her the right to take away my daughter?" Lindemulder said. "You know, this is my daughter. I am the best mother I can be."
Lindemulder, who has appeared in more than 100 adult films, acknowledged making "horrific choices in the past," but says her life is back on track and that she deserves to keep custody of her daughter.
Bullock and James have called Lindemulder and her new husband, also a convicted felon, unfit.
In a letter to the judge at Lindemulder's sentencing, Bullock raised concerns about the girl's safety, alleging that the child was left alone during the day while Lindemulder was "asleep from drug use."
CLICK HERE to read the full text of Bullock's letter.
"I myself have stopped working like I used to in order to be here with Jesse and the kids because we are on constant high alert," Bullock wrote, "never knowing what condition Janine will be in, and even more concerning, the condition [the girl] will be in."
Lindemulder, 40, has admitted to substance abuse in the past but said there have been long stretches of time when she hasn't used any drugs.
"Sandy doesn't know what goes on in my house," she said. "I'd love for her to. Please come over, you know, I'll make dinner, you know, let's sit down, [as] two women."
Bitter Battle Over Fate of 5-Year-Old Girl
In her letter, Bullock defends her motive for wanting sole custody and denies the assertion that it is rooted in her inability to have children. "I am aware that Janine has claimed many times that my desire to have [the girl], was because I could not have children of my own," Bullock said, adding, "that couldn't be farther from the truth."
"I know the term 'stepmother' carries many connotations, one of them being 'glorified babysitter,'" Bullock wrote. "My commitment and responsibility to [the girl] ... goes beyond that."
Lindemulder said, "I didn't say that. But I do believe the reason Sandra is so interested in Sunny ... she [thinks she] is saving Sunny from me, from her own mother. ...That's what I believe."
Jesse James also wrote to the judge, blasting his ex-wife's lack of responsibility in paying her taxes and her lifestyle.
CLICK HERE to read the full text of James' letter.
"I believe that Janine should not be shown any leniency in her sentence," he wrote.
It's an interesting battle for the couple to wage. Before marrying James, Bullock, now 45, never expressed interest in becoming a mom, telling People magazine in 2005, "If I did have kids my entire life would shift. I would no longer act or be in magazines."
But now it seems fame and fortune aren't enough. In March, Bullock hinted in an interview with InStyle magazine that she regretted not having had children."If I waited too long, it's because we were supposed to do other things," Bullock told the magazine. "If it is just too late ... there are millions of children on this planet that I would be honored to call my own."
"She's been very frank about the fact that she chose her career rather than having children," said Albert Lee, Us Weekly's deputy news editor. "She's talked about how her mother always taught her to choose career over family. In that respect, she was certainly successful. She's one of the few women who can earn an eight-figure salary per movie, especially at that age."
According to Parade magazine's latest issue and court documents related to the custody case, Bullock has become close to James' three children from previous marriages, particularly with his 5-year-old daughter who is at the center of the custody dispute. Bullock tells Parade that she can't imagine life without the little girl.
"The universe put this in our lap," Bullock said. "I seemed to have stepped in right when I needed to be there. I now know that anything sweet, really sweet, that I have was nothing that I planned. If you don't have kids and animals, you don't truly know what real life is about."
But Bullock's latest role as a stepmother embroiled in a custody fight with James' ex-wife has been anything but sweet.
Stormy Relationship Between Jesse James, Janine Lindemulder
Before tying the knot with Bullock in 2004, James was married to Lindemulder for one year. He left Lindemulder when she was seven months pregnant with their daughter, her lawyer, Ron Hoevet, told the Orange County Register. Hoevet represented Lindemulder when she was ordered to pay almost $300,000 in outstanding taxes last year and served the six-month prison term.
Lindemulder has since spent six months in a halfway house and, according to court documents obtained by ABC News, has rented a "low-end three bedroom home in a fairly undesirable neighborhood in Hollywood." Lindemulder stated that it is the best she could do "because of her poor credit" and an order stating "I am not allowed to work in the adult [entertainment] industry, which is all I've ever done for the past 23 years."
Experts say keeping custody could be an uphill battle for Lindemulder.
"She's a former porn star, she's a convicted felon, she's done custody time, she's up against huge star power," said Dana Cole, a Los Angeles attorney. "Ultimately, though, a judge has to look at the big picture and understand that the child has the right to know both parents.
"Bitter custody disputes are actually not that uncommon. They happen every day in the courts, and judges have to balance out the competing factors."
Lindemulder said she would like to live near her daughter's school in Costa Mesa, Calif., so she can become be a "good co-parent with Jesse and stepmother Sandra." In a long letter to the court, she said, "My daughter and I are both very eager to get back to normal" and requested financial aid. "Possibly Jesse [James] can sign for a proper home for [the girl] and I." But according to court documents, it didn't look as if that was going to happen anytime soon. Lindemulder and James were ordered to meet with a court mediator in the custody dispute later this month.
Indeed, while Lindemulder was set to regain custody after completing her prison sentence, James went before a judge to determine whether she was a fit mother. According to a court declaration, James asked that Lindemulder prove that she could provide a safe environment for their child that included keeping her away from pornographers, drug addicts, guns and firearms, felons and other unsafe environments.
James portrayed Lindemulder as emotional and erratic, saying she sent taunting text messages to James one moment and writing "I WON'T BE AROUND. YOU GUYS WIN. I CAN'T TAKE" and "U WIN, FICKIN WIN," and then apologizing for her behavior. Court documents confirmed that she did apologize for the messages but also indicated she has other problems.
James, in his declaration, said that Lindemulder kept her marriage to Jeremy Aikman, "a two-time state and federal felon," a secret from him and the court. The judge in the case recently amended Lindemulder's visitation order to state that Aikman must stay away from the little girl. Court records indicated that Aikmen had recently left prison and had a record of several convictions involving alcohol, guns and manufacture of narcotics.
A source involved in Lindemulder's legal issues and dealings with James told ABCNews.com that Lindemulder was "not in favor of the divorce when Jesse left. Janine had custody of her daughter. Jesse didn't see his daughter for the first two years of her life except for around the time when she was born. It was only after he got involved with Sandra Bullock that he decided he wanted to have a relationship with his daughter."
The source added that "the only reason Jesse got temporary custody was because Janine had the tax problem, and the court order said that custody would revert to Janine when she finished serving her time. One of the things that was really vicious was that both Jesse and Sandra Bullock wrote letters to the court in [Lindemulder's] tax case urging the judge to put her in jail so they could use that as an advantage. They claimed that because she was in the porno industry and abused drugs, she should be put in jail, but the fact was she passed drug test.
"They used a misdemeanor tax offense to gain advantage," the source concluded. According to court papers, James did accuse Lindemulder of drug abuse, and although she admitted to a long-term cocaine problem in the past, she passed a court-ordered drug test administered before she went to prison for tax evasion.
Lindemulder, who has a son named Tyler from her 1988-1996 marriage to a construction worker, didn't start off in the porn industry. After some attempts at mainstream movie stardom, the tattooed blond beauty made a name for herself in lesbian adult films in the 1990s with the adult film company Vivid.
Soon after dating Motley Crue lead singer Vince Neil, a sex tape surfaced of the couple and former Penthouse model Brandy Ledford. The tape was eventually distributed by the same company that released Pamela Anderson and Tommy Lee's now-infamous honeymoon sex video.
Lindemulder is perhaps best known because of her association with the punk band Blink 182. She graced the cover of its 1999 album "Enema of the State" and appeared in two of the band's videos.
She now said she's searching for a career in the tattoo business and said that despite the recent situation, she believed Bullock was an excellent mother who cared deeply about her daughter.
ABCNews.com's and "Good Morning America's" multiple calls and e-mails to Bullock's publicist and James' attorney were not returned. Bullock's attorneys said they had no involvement in the case.
ABCNews' Eileen Murphy contributed to this report.