Chancellor Alistair Darling has tried to reassure Labour MPs that low paid workers who will be hit by the scrapping of the 10p tax rate will get compensated for their losses.

The Labour tax rebel row threatened to erupt again after Treasury Chief Secretary Yvette Cooper suggested that only the compensation package for pensioners under 65 would be backdated.

Her intervention drew an angry rebuke from tax rebel leader Frank Field, who accused her of being "badly briefed".

In an interview with the BBC Radio 4 programme, he insisted that he had assurance from Prime Minister Gordon Brown that the entire package, including younger workers with no children, would be backdated to April 1 - the start of the current tax year.

And he warned that MPs would "not take kindly to any attempt to tamper with the deal" which he had hammered out with ministers.

"This is an agreement that the Prime Minister actually put his stamp on. There will be a compensation package, it will be backdated. This is a package that I am sure the Government will want to fall into line with."

Mr Darling said that losses suffered by low paid workers this year as a result of the tax changes would be "offset" - although he refused to use the word "backdated".

"Our focus is to ensure that we allow the average losses from the abolition of the 10p band to be offset for this year," he said.

His comments appeared to reassure Labour MPs, but nevertheless, the row underlined the mood among MPs after Mr Brown's dramatic climbdown in the face of a catastrophic Commons revolt.

Under the plan set out by Mr Darling, the Government will seek to help the two main groups to be hit by the scrapping of the 10p rate - pensioners under 65 and younger workers with no children.

Tory leader David Cameron said the Government had descended into a "complete shambles".

"Even when it comes to making a u-term, this Government is incompetent. With this Prime Minister and with this Chancellor you have always got to check the small print," he said.

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