Two government watchdog groups asked the House ethics committee Thursday to appoint an independent counsel to investigate a complaint that House Majority Leader Tom DeLay (search) traded political contributions for legislative favors.

A spokesman said DeLay opposes the groups' request.

The groups said an independent investigator is needed because four members of the committee received political contributions from DeLay and because DeLay, as the second-highest ranking member of the House, wields significant power over the members.

"Mr. Delay's stature as one of the most powerful members of Congress — with the capacity to extract retribution from anyone — makes it especially difficult for his peers to sit in judgment of him," said Common Cause president Chellie Pingree. Citizens for Responsibility and Ethics in Washington, which helped prepare the complaint against DeLay, also made the request.

The groups pointed out that independent counsels were named to investigate former House Speakers Newt Gingrich (search), a Republican and Jim Wright (search), a Democrat, when they ran into ethics troubles.

Two DeLay aides attended the news conference to counter the claims made by the groups. DeLay aide Jonathan Grella handed out documents detailing contributions by Democrats to the ethics committee members and by the watchdog groups to Democrats.

"We have full confidence the ethics committee will handle this in a proper matter," Grella said. He said the groups "make their living" complaining about Republicans.

The ethics committee, officially known as the House Standards of Official Conduct Committee, is reviewing the complaint submitted by Rep. Chris Bell (search), D-Texas. It should decide by early next month whether to launch an investigation, dismiss the complaint or take more time to review it.

Bell charges in the complaint that DeLay illegally solicited and accepted political contributions from Kansas-based Westar Energy Corporation in return for legislative favors and laundered illegal corporate contributions for use in Texas elections. In a letter sent Wednesday, Bell also asks the committee to investigate DeLay's solicitation and acceptance of contributions from Enron to be used in Texas, as detailed in Enron e-mails.

DeLay has said Bell filed the complaint because he is bitter over losing his re-election primary. Bell was forced to run in a district redrawn by Republicans. DeLay has until July 22 to formally answer the complaint.

Last week, DeLay hired attorney Ed Bethune, a former Arkansas congressman who represented former House Speaker Newt Gingrich in his ethics case.