A watchdog group filed a complaint with the Federal Election Commission against Ralph Nader (search) on Friday, saying the independent presidential candidate is violating federal campaign laws by accepting office space and telephone service from a public charity he created.

Citizens for Responsibility and Ethics in Washington alleges that Nader's campaign is renting valuable space at below-market prices from Citizen Works, an activist group that supports progressive causes.

The complaint also says Citizen Works and the Nader campaign share a common receptionist and several telephone lines.

The watchdog group also filed a complaint with the Internal Revenue Service (search) alleging that Citizen Works is violating its status as a charitable organization by benefiting the Nader campaign. The IRS complaint asks the agency to enjoin Citizen Works from offering any further assistance to the campaign.

"Ralph Nader seems to think that because he founded Citizen Works (search), he can use the organization as he sees fit," said Melanie Sloan, the watchdog group's executive director. "This includes using the charity to assist his campaign. No one, not even Ralph Nader, is exempt from campaign finance and tax laws."

Questions about the rental arrangement were first raised in a March 15 story by Joe Conason in the online magazine Salon. Nader has denied any wrongdoing.

Nader spokesman Kevin Zeese called the allegations "totally false" and described the lawsuit as "completely frivolous and without merit."

Zeese said the two organizations do not share phones and that a check with the building's landlord revealed the campaign is actually paying above market rates for the space.