Peter Hain bought time in his fight for political survival yesterday, when he emerged from two lengthy Commons sessions damaged but not yet finished by the donations row.

Gordon Brown finally gave an unequivocal vote of confidence to the Work and Pensions Secretary after two earlier attempts this week to shore him up failed to do the trick.

The Prime Minister’s remark in an ITV interview on Tuesday that Mr Hain had admitted “an incompetence” was seized upon gleefully by critics, even though Mr Brown had clearly voiced the hope and expectation that he would stay in office.

But Mr Hain, who has apologised to the whole Cabinet for the problems he has caused, is still facing an uphill struggle, his short-term future dependent upon the outcome of an inquiry by Commons authorities into his failure to register £103,000 in donations.

Mr Brown would find it hard to keep him if he was severely censured or even suspended as a result, and many backbenchers think it unlikely that he could stay in government beyond Mr Brown’s next big reshuffle.

The Prime Minister is supporting Mr Hain and does not want to be seen to surrender to media calls for him to go. He told MPs yesterday: “When it comes to the work of the Secretary for Work, unemployment is down, employment is up.

“Single parents – more are in jobs – less people are claiming incapacity benefit. There are more long-term unemployed getting back to work and since he became Secretary of Work and Pensions there have been hundreds of contracts signed with local employers to get thousands of people back to work. And that is why I have confidence in what he is doing.”

Mr Brown’s spokesman also insisted that the Prime Minister was talking of the management of Mr Hain’s campaign when he talked of “an incompetence” in failing to declare the donations to the Electoral Commission.

Nick Clegg, the Liberal Democrat leader, said: “When Gordon Brown said he wanted a government of all the talents, no one realised that incompetence was going to be one of them.

“Whatever the Electoral Commission now decides, Peter Hain’s political credibility lies in tatters.”

Mr Hain faced Commons questions in his other role as Welsh Secretary, including criticism of his endorsement of a company whose boss had contributed to his deputy leadership campaign. He was barracked when he said he “absolutely no regrets”.

Mr Brown chatted to Mr Hain when he entered the chamber for Prime Minister’s Questions.

Later Mr Hain appeared in a hastily arranged Conservative-inspired debate on illegal immigration.

The Conservative spokesman Chris Grayling said it “all appears to be getting a bit much” for Mr Hain. Mr Hain replied that Mr Grayling was “far more interested in making political points” than dealing with illegal workers. The debate followed claims that 6,500 illegal immigrants employed as security guards were given national insurance numbers.

Mr Grayling said this was the “tip of the iceberg” and he accused the Government of handing insurance numbers to “tens and possibly hundreds of thousands” of illegal immigrants. “Some people might call that incompetence,” he added. “Just when the Secretary of State thought that things could not get any worse, the chaos spreads to another part of his job.”

At the same time, Mr Grayling added, Mr Hain “could not sort out the confusion with his campaign finances because he was too busy getting on with his two jobs in government – what a state of utter chaos”.

Mr Grayling asked: “Can you now tell us why you believe you are still the right man to do the job?”

Mr Hain accused Mr Grayling of framing the debate under a “false premise”. He said that the Government had introduced new checks and controls on the issuing of national insurance numbers to foreign workers. The official election watchdog was urged to investigate fund-raising “patrons’ clubs” linked to Tory MPs in the latest twist in the donations row.

Labour MPs John Mann and Kevan Jones have submitted a formal complaint to the Electoral Commission about clubs linked to 80 Conservative MPs or their constituency parties. They include 13 members of the Shadow Cabinet, or their constituencies, including David Cameron and George Osborne, the Shadow Chancellor.

In a letter to the Commission, Mr Mann and Mr Jones said that none of the clubs concerned appeared to have been registered under the Political Parties, Elections and Referendums Act.

They also complained that there was no evidence that donors to the clubs had been checked to ensure that they were permissible donors.

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