The worst spill in US history has been

Barton offered another apology to his Republican colleagues at a meeting this morning, telling them he regretted apologizing to BP and sparking a political firestorm, aides said. His mea culpa, they said, appeased Minority Leader John Boehner of Ohio and other Republican leaders.

The Republicans' decision to leave Barton in place will likely continue to fuel Democrats' efforts to paint the GOP as a friend of "Big Oil," but it avoids a messy intramural fight.

"Not much use removing him now and creating a whole lot of infighting," a senior Republican aide said.

But the move does not assure Barton's return to the committee's ranking member seat in the next Congress, or the panel's chairmanship, if his party regains control of the House. Republicans enforce a three-term limit on ranking members and chairmen, and Barton's time will be up.

Barton -- who chaired the Energy Committee when it drafted the 2005 energy bill that encouraged more offshore drilling -- had been expected to seek a waiver of the three-term rule. But that move seems next to impossible after Barton's fateful televised apology to BP CEO Tony Hayward at a hearing Thursday.

Hours later, Barton said his comments were "misconstrued," before later retracting the original remarks in a statement distributed by Republican leadership.

The two Republicans considered most likely to replace Barton next year are Michigan's Fred Upton and Illinois' John Shimkus. Upton is considered the leader in that race, largely because leaders fear the more junior Shimkus is more prone to shooting from the lip.

Since 1989, the oil and gas industry has contributed $184,150 to Upton, making it 12th among industries that have given to his campaigns, according to Opensecrets.org.

The petroleum industry is more generous to Shimkus, contributing more than $240,000 to his campaigns since 1996, ranking it fifth among industries who have contributed to him.

Oil and gas interests have been the top contributors to Barton, who hails from the Texas oil patch. They have donated more than $1.4 million to him since 1989, according to OpenSecrets.org.

The political risks from the disaster were underscored by a poll showing Barack Obama's job performance rating has dropped to the lowest level of his presidency. The Obama administration is appealing a court ruling blocking a six-month moratorium on deepwater drilling.

The worst spill in US history has been thrust to the top of Obama's crowded domestic agenda but the Wall Street Journal/NBC News poll found half of those surveyed disapproved of his handling of the spill.

Overall Obama's rating stood at 45% in the poll, down five points from early last month. For the first time in the survey, more people, or 48%, said they disapproved of his job performance.

The administration sought to keep its responses to the catastrophe in play as it appealed against the lifting of a deep-water drilling ban. A judge had said the moratorium was too far-reaching and not adequately justified despite the spill.

The government also asked district judge Martin Feldman in New Orleans to put his ruling against the moratorium on hold pending the outcome of the appeal or until the appeals court can consider a request for a stay.

The justice department said the temporary moratorium affected only 33 active deepwater drills in the Gulf of Mexico.

In addition to the appeal, interior secretary Ken Salazar said he would revise his original order suspending drilling 500ft below sea level to make it more flexible and thus address the court's concerns.

The government imposed a six-month moratorium on deepwater drilling after the offshore rig exploded on 20 April killing 11 workers and rupturing BP's well.