Campaign finance reformers in the House and Senate introduced new legislation Wednesday to regulate outside political interest groups that were not covered in the campaign finance reform legislation they ushered into law in 2002.

Sens. John McCain (search), R-Ariz., and Russ Feingold (search), D-Wis., as well as Reps. Marty Meehan (search), D-Mass., and Chris Shays (search), R-Conn., say they're confident they'll be able to pass legislation that would prohibit so-called 527 groups from using unregulated soft money to fund ad campaigns attacking or supporting federal candidates. However, McCain said Congress is unlikely to get to it in the remaining days of the 108th Congress. He expressed optimism that the bill would get a full airing next year in a new Congress.

Under their bill, 527s (search), named after their place in the tax code, would still be able to use some of their unlimited soft money on voter mobilization efforts, but activities would have to be paid for with at least 50 percent of regulated and limited hard money.

The sponsors said the legislation would also require the groups that register with the IRS as partisan political organizations accept only limited donations from individuals and disclose their donations and spending to the Federal Election Commission (search).

The proposal exempts groups that raise less than $25,000 or spend only on nonfederal elections, on state or local ballot initiatives or on the nomination or confirmation of people to non-elective offices such as judgeships.

The 2002 McCain-Feingold campaign finance law banned national political parties and candidates from raising and using soft money, starting with this election cycle. But the lawmakers said the FEC is not doing its job of adequately enforcing the laws with matching regulations.

"McCain-Feingold is working but not as well as it should because the FEC is trying to find a way of circumventing it ... the FEC has given these [527] groups cover," Shays said.

McCain said the next step will be to reform the FEC.

"Their conduct has been disgraceful beyond belief," he said, later adding, "we will start on our effort to reform the FEC early next year."

"Sometimes it seems a little bit like our mission in life is to clean up the mess that the FEC has made," Feingold said at a news conference on the proposal.

The FEC so far has declined to limit fund-raising and spending by certain groups in this year's election, with some commissioners saying they believed only Congress had the authority to do so. Several complaints are pending at the commission over the soft money spending.

Several outside groups began massive advertising campaigns and get-out-the-vote activities this election cycle using soft money, particularly on the Democratic side. The groups argue that their activities are legal because they stop short of calling flat-out for a candidate's election or defeat.

The campaign finance reformers were joined by Sen. Joe Lieberman (search), D-Conn., a sponsor of previous legislation aimed at outside groups.

FOX News' Julie Asher and The Associated Press contributed to this report.