Pressure on Veterans Affairs Secretary Eric Shinseki to resign increased today after an inspector general's interim report found that inappropriate scheduling practices have been "systemic" throughout the VA.

For the first time, Democrats in the House and Senate joined Republicans in issuing new calls for Shinseki to step down from his post leading the VA after the release of the report.

"The inspector general's preliminary report makes it clear that the systemic problems at the U.S. Department of Veterans Affairs are so entrenched that they require new leadership to be fixed. Secretary Shinseki must step down," Sen. Mark Udall, D-Colo., said in a statement. "We need new leadership who will demand accountability to fix these problems and ensure the VA is providing Coloradans the services they've earned."

"The Inspector General's report confirms the worst of the allegations against the VA and its failure to deliver timely care to veterans," said Sen. John Walsh, D-Mont. "It is time for President Obama to remove Secretary Shinseki from office."

Udall and Walsh were just the vanguard of a growing number of Democrats who called for Shinseki to step down, in addition to Republicans who were previously on the fence.

"It's time for Secretary Shinseki to step down," Sen. John McCain, R-Ariz., said during a news conference in Phoenix today. "If Secretary Shinseki does not step down voluntarily, then I call the President of the United States to relieve him of his duties and fire him."

"General Shinseki has given his life to serving this country and for that, we are in his debt," said Rep. Buck McKeon, chairman of the House Foreign Affairs Committee. "However, the problems at the Department of Veterans Affairs have grown beyond what this nation can bear. I believe America's veterans would be best served with a fresh set of eyes on the VA system. Only new innovations and aggressive reform can get the problems at the VA under control."

"It would be best if General Shinseki stepped down as Secretary, both as an example for other VA leaders and to lay the groundwork for new leadership to meet with success," said McKeon, R-Calif.

Rep. Jeff Miller, chairman of the House Committee on Veterans' Affairs, also called on Shinseki to resign. "Shinseki is a good man who has served his country honorably, but he has failed to get VA's health care system in order despite repeated and frequent warnings from Congress, the Government Accountability Office and the IG," said Miller, R-Fla.

"What's worse, to this day, Shinseki - in both word and deed - appears completely oblivious to the severity of the health care challenges facing the department," Miller added, noting the "VA needs a leader who will take swift and decisive action."

"Sec. Shinseki has proven time and again he is not that leader. That's why it's time for him to go," Miller said.

In addition to calls for Shinseki's resignation, lawmakers are asking for the Department of Justice and FBI to conduct a criminal investigation into the allegations that delayed care may be responsible for the deaths of veterans.

"These allegations are not just administrative problems. These are criminal problems," McCain said.

The growing chorus of calls for Shinseki's resignation has mostly emanated from Republicans on Capitol Hill. Udall became the first Senate Democrat to demand Shinseki's resignation. In a letter to Shinseki, Sen. Joe Manchin, D-W.Va., warned that patience among lawmakers is "vanishingly thin."

"While I have not yet joined in calls for your resignation, I assure you that patience in Congress for what we perceive as inaction on the part of the VA to immediately and fully address these issues is vanishingly thin," Manchin wrote.

In a statement today, Shinseki said the IG's findings were "reprehensible to me, to this Department and to Veterans."

President Obama was briefed on the IG's interim report today by White House Chief of Staff Denis McDonough, White House Press Secretary Jay Carney said.

"The President found the findings extremely troubling," Carney said. "As the President said last week, the VA must not wait for current investigations of VA operations to conclude before taking steps to improve care. It should take immediate steps to reach out to veterans who are currently waiting to schedule appointments and make sure that they are getting better access to care now."

"The Secretary has said that VA will fully and aggressively implement the recommendations of the IG. The President agrees with that action and reaffirms that the VA needs to do more to improve veterans' access to care," Carney said.

Shinseki met with President Obama last week to discuss the problems at VA facilities. Shinseki later told reporters that he did not submit his resignation to the president.

ABC News' Devin Dwyer and John Parkinson contributed to this report.