The immediate financial cost may be small, but the political price will be large. Yesterday’s deal between the Government and Labour MPs over the abolition of the 10p starting rate of income tax was predictable and inevitable. Neither side wanted to risk pushing the issue to the brink in the key Commons vote next Monday, three days before the local elections.

So in good trade union fashion, a facesaving formula was agreed. At one level, the Government has not conceded that much. It has not had to rewrite this year’s Finance Bill, as Alistair Darling has insisted. But he has mainly offered promises, and reviews about how to help low-paid workers without children and pensioners under 65, through direct payments or changes to tax credits. For pensioners aged 60 to 64, the search is to see whether losers from the end of the 10p rate can be helped by the mechanism that exists to pay the winter fuel allowance. For others outside tax credits, the focus is on potential changes to this system, and, for younger workers, alterations to the minimum-wage regime.

All this is vague. There is no estimate of cost, nor is it clear how these diverse goals can be achieved.

The position will not be clarified until the Pre-Budget Report this autumn.

The key words in Mr Darling’s letter that ended the revolt were: “We do no wish to wait unnecessarily until November – whatever conclusions we come to, all the changes will be backdated to the start of this financial year.”

The Labour rebels can claim to have shifted the Government. Gordon Brown has had to eat a lot of his recent words. It is less than a week ago, on his American trip, that Mr Brown was playing down the number of losers and dismissing the scale of any rebellion. He moved into “I feel your pain” mode only on Monday, and then to accept that any concessions would have to be backdated. In a display of Presbyterian chutzpah, he belittled the value of the 10p band, which he himself had introduced.

Voters care more about outcomes than climbdowns. But this has been a voter-generated row. Any Labour MP will tell you of the large number of angry letters received from constituents, including many not directly affected. The move appeared unfair, however much Mr Brown talks about the much larger numbers of families with children and pensioners who are better off. And compensation will not be paid for several months. The damage here could be serious, and lasting, since it is core Labour voters and activists that have been most upset. A key indicator will be the turnout in safe Labour working-class areas on May 1.

Mr Brown’s leadership has been seriously damaged. His failure to appreciate for so long the depth of grassroots feeling and then his eventual concession have reinforced Tory charges about a ditherer. Labour loyalists talk of a turning point, showing that Mr Brown is, at last, willing to listen to backbenchers. Perhaps. But critical MPs will feel that having forced him to shift once, they may succeed again, over 42 days’ detention without trial. That is why Mr Brown was so keen last night to demonstrate his determination to be tough, as on public sector pay. Yesterday he got out of a largely self-inflicted difficulty. Now he has to reestablish his authority.

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