A hard-hitting new TV ad from the Obama campaign accuses Mitt Romney of profiting from and indirectly supporting "sweatshop conditions" at a Chinese appliance company in which his Bain Capital invested.

"A company called Global Tech maximized profits by paying its workers next to nothing under sweatshop conditions in China," the ad says, over file-photo images of distressed-looking Chinese factory workers.

"When Mitt Romney led Bain," it continues, "they saw Global Tech as a good investment, even knowing that the firm promoted its practice of exploiting low-wage labor to its investors."

The attack, ahead of the first presidential debate Wednesday, comes as Democrats renew scrutiny of Romney's foreign investments and private-sector business record at Bain, which the Republican nominee has made a centerpiece of his campaign.

The ad will begin running this week in New Hampshire, Virginia, Florida, Ohio, Iowa, Colorado, and Nevada - all states with sizable manufacturing sectors - the Obama campaign said.

Romney's ties to Global Tech were first documented last month in a Boston Globe report that noted the appliance-maker promoted itself to investors by touting "inexpensive labor" as a top selling point. A 1998 company prospectus reviewed by the Globe also promoted the fact that the appliance-maker had an "overall effective tax rate that may be less than that of U.S. corporations."

Bain capital affiliate Brookside Capital Partners Fund, which listed Romney as its president and CEO at the time, bought a 6 percent share of Global Tech, according to Securities and Exchange Commission documents reviewed by the paper and ABC News.

The Obama campaign has seized upon the report to claim that Romney's investment activities facilitated the outsourcing of American jobs and working conditions many Americans would find deplorable. The prospectus obtained by the Globe described six-day work weeks with two 10-hour shifts per day and dormitory facilities that housed 3,700 workers.

Independent fact-checkers have, however, noted that there is no evidence Romney had an active role in sending any American jobs to China or in approving the specific investment in Global Tech.

"This is another 'overboard' ad from a president who is trying to distract from his failure to stand up to China," Romney spokeswoman Amanda Henneberg told ABC News.

"Four years ago, then candidate Barack Obama promised to take China to the mat, but refused to label China a currency manipulator because he didn't want them to be embarrassed," she said. "President Obama's failure to stand up to China has cost our country jobs and is one more reason that we can't have four more years like the last four years. Mitt Romney will stand up to China, label them a currency manipulator, protect our intellectual property, and ensure that more jobs stay in America."