The Senate's healthcare bill would lose 12 Democratic votes in the House, Rep. Bart Stupak (D-Mich.) said Wednesday.

Stupak, the sponsor of an amendment to the House healthcare bill that barred federal subsidies for health plans covering abortion, said that 12 lawmakers who had previously supported healthcare reform legislation in the House would be ready to switch.

"It's accurate to say there are at least 12 of us who voted for healthcare that have indicated to the speaker and others that unless you change this language, we will vote against it," Stupak said during an appearance on MSNBC.

Stupak and other Democrats who oppose abortion have threatened to fell the healthcare effort before Congress over the issue of abortion. They say the Senate's provision, which had been demanded by centrist Sen. Ben Nelson (D-Neb.), does not go far enough in preventing federal money from going to support abortion.

The congressman's comments come on the heels of his claims last week, when he said he knows of 15-20 Democratic lawmakers who are witholding support for the bill because of "other problems." But it is not clear if or how many overlap between the two groups.

The Michigan Democrat said he'd spoken to House Speaker Nancy Pelosi (D-Calif.) about the prospects of a "sidebar" bill on abortion that would be tied to the final healthcare bill.

"It would have to be a separate bill; you could sidebar it to the final bill," he said. "One bill doesn't pass without the other. They walk down the aisle together."

Pelosi will have to get 216 votes together to pass her healthcare bill after retirements and resignations have left some vacancies in the House. She passed the House health bill in November with a couple of excess votes, but that was only after adopting the Stupak amendment in order to placate centrists with concerns on abortion.

Stupak said he still suspected, though, that Democrats wouldn't allow their health reform efforts, one of their top domestic priorities, to go down over concerns on abortion.

Jordan Fabian contributed to this post.