An ethics watchdog group asked the Federal Election Commission and the Internal Revenue Service yesterday to investigate an arrangement between Ralph Nader's presidential campaign and a charity that he created.

Nader and the charity, Citizen Works, committed "direct and serious violations of campaign finance law" when the campaign rented space and accepted phone service from the charity, according to a complaint filed with the FEC by Citizens for Responsibility and Ethics in Washington (CREW).

In a separate letter to the IRS, the ethics group charged that Citizens Works, a charity formed in 2001 by Nader and the manager of his presidential campaign, Theresa Amato, breached its tax-exempt status by renting office space to Nader's campaign below market rate and by providing services for which the charity was not reimbursed.

Tax law prohibits public charities from aiding political campaigns. Violations can result in a charity losing its tax-exempt status. In addition, campaign finance law requires candidates to account for all contributions, including non-monetary donations.

Nader has denied that he broke any laws. He said that he paid market rate for the office space, had separate phone lines and vetted the arrangement with an outside lawyer.

In reply to the complaints, the campaign said in a statement, "There is no merit whatsoever in these filings."

Citizen Works spokesman Lee Drutman said he had not seen the complaint. The Citizen Works Web site states, "Citizen Works has provided no assistance, direct or indirect, to the 'Nader for President' Campaign or his presidential exploratory committee."

Melanie Sloan, executive director of CREW and a former federal prosecutor, said she filed the complaint in response to a June 13 Washington Post article that documented several links between the campaign and the charity.

The Nader campaign, in its statement, referred to the Post report as an "article of innuendo" and said that the group's complaints contained no original research.