Democrats and Republicans blamed each other on Friday for an impasse that has suddenly left the U.S. House of Representatives unable to conduct possible ethics investigations of its own members.

The 10-member ethics committee — five Democrats and five Republicans — deadlocked late on Thursday on a vote to adopt new Republican rules that would make it tougher to launch an ethics investigation. A majority is needed to adopt the rules.

“The sincerity of our objections to these rules and the extent that they would undermine the ability of the ethics committee to do its job has got to be appreciated by the majority,” Rep. Alan Mollohan of West Virginia, the panel’s top Democrat, said on Friday.

“We understand Democratic members are frustrated,” said Ed Cassidy, a top aide to Chairman Doc Hastings, a Washington state Republican. “But we’re hopeful we can persuade them that the ethics committee has no choice but to enforce the rules as passed by the full House.”

The rules were approved in January by the Republican-led House after Majority Leader Tom DeLay of Texas was admonished by the ethics panel on three separate matters in 2004.

The new rules, which proponents say would treat targets of probes more fairly, require a majority on the ethics committee to authorize an investigation of possible misconduct. Previously, a tie vote would automatically trigger an inquiry.

Last month, House Speaker Dennis Hastert, an Illinois Republican, shook up the committee by naming Hastings chairman and putting two contributors to DeLay’s defense fund on the panel.

The action prompted complaints that Republicans were trying to shut down ethics enforcement.

Mollohan said of the committee impasse over rules, “We’re just going to have to work our way through this.”

Ron Bonjean, a Hastert spokesman, said, “Democrats have chosen to shut down the ethics committee. The only way to get over this impasse is for Democrats to put the ethics process above partisan politics.”