British Prime Minister Gordon Brown made concessions on tax reform on Wednesday to end a rebellion by members of his own party which had threatened to further erode his authority.

The government said it would look at ways of helping those worst affected by the abolition of the lowest income tax band and backdate any additional payments to the start of the tax year in April.

Frank Field, the leader of the Labour rebels, withdrew an amendment which had raised the prospect of a humiliating defeat in a parliamentary vote next week. "The government has listened," Field said.

However, the opposition Conservatives, leading in opinion polls, tore into Brown over his "panic" concession after he had repeatedly said the abolition of a 10 percent tax rate band was fair and did not hurt the poor.

In heated exchanges in parliament, Conservative leader David Cameron accused Brown of a U-turn and said he was "a pathetic figure" suffering a massive "lack of authority".

Brown, who replaced Tony Blair as prime minister last June after 10 years as finance minister, has seen his ratings slide as the effects of the credit crunch dent his reputation for sound economic management.

In the latest challenge to his authority, nearly 50 Labour lawmakers had demanded concessions to help low earners hurt by the tax changes.

The timing of the row could hardly have been worse - local elections are scheduled on May 1, Brown's first test at the ballot box since taking over from Blair.

Speculation has increased that a challenger for Brown's job could soon emerge if the party keeps trailing in the polls.

CONCESSIONS FOR POOR

The abolition of the 10 percent tax rate was part of Brown's last budget as finance minister in 2007 and was intended to fund a reduction in the main tax rate to 20 percent from 22 percent.

It was unclear how the concessions outlined on Wednesday would be paid for. Getting rid of the 10 percent tax rate band raises some 7 to 8 billion pounds ($13.9-15.9 billion).

"We are determined to take action because we are the party of fairness," Brown said in parliament to loud cheers from his supporters.

Finance minister Alistair Darling said he would look at winter fuel payments for the elderly, tax credits and the minimum wage as ways to reduce pressure on people who will suffer from the change.

The infighting has been damaging for Labour, reminiscent of the feuding that kept them out of power for almost two decades until Blair led them to electoral success in 1997.

Labour, more than half way through its third consecutive term in office, lags the Conservatives in the polls and Brown's personal popularity ratings have plummeted. He does not have to call a general election until mid-2010.