The committee plans to file suit Monday, asking the U.S. District Court in Washington to order the Federal Election Commission to investigate McCain's decision to reject public financing for the primary, The New York Times reported.

The six-member commission has four vacancies and is unable to take any action because it cannot meet with a quorum. The Democratic majority in Congress has objected to some of President George W. Bush's reappointments.

Joe Sandler, a lawyer for the Democrats, said if the commission remains without a quorum the committee will ask the court to allow a suit against the McCain campaign.

McCain's fundraising picked up when he became a favorite in the battle for the Republican nomination, and he is now over the $54 million limit for candidates who use public funds. When his fortunes were at a low ebb, he obtained a $4 million loan, secured by the assumption he would be getting public funds.