UK - Peter Hain, Secretary of State for Work and Pensions, should either explain his actions "convincingly" or leave his post, following scandals behind the funding of his attempted election as party deputy leader, the UK's opposition leader David Cameron has warned.

Leader of the Conservative Party today commented on Hain's failure to answer questions about donations of more than £103,000 to his deputy leadership campaign, which were declared to the Electoral Commission after the required deadline.

Neither the Conservatives or Liberal Democrats have yet called for Hain's outright resignation, but pressure is building on the DWP and Wales Secretary as a statement from the Minister failed to placate Plaid Cymru, the Welsh nationalist party, who continued to state Hain's position is "untenable".

Hain, the fourth Work & Pensions Secretary in less than three and a half years, said on Saturday he had apologised "unreservedly" to both the Electoral Commission and the Parliamentary Commissioner for Standards for the late declaration of monies.

He also apologised for "the embarrassment caused by poor administration and lack of early and clear disclosure" but denied that he had anything to hide and claimed all donations were from people and organisations which were "eligible and legally entitled" to contribute.

But Cameron today warned: "When you're in a situation where there are a huge number of questions, the sensible thing is to get out there and explain yourself, answer the questions and apologise where necessary. What is unacceptable is to hide away and avoid being interviewed.

He has a choice, he has to explain himself or he will have to leave the cabinet," added Cameron.

Elfyn Llwyd, Westminster group leader for Plaid Cymru, added: "The statement by Peter Hain was largely self-serving. He was gracious enough to apologise and he said that he would comply fully with the Electoral Commission and the commission for standards but that is what would be expected of an MP in any event.

"Public confidence in Peter Hain has been severely damaged and his position, I believe, remains untenable."

Gordon Brown, prime minister, has continued to support Hain. However, he has admitted the decision on whether Hain should keep his job would depend on the findings of an inquiry by the Parliamentary Commissioner for Standards.

That said, if the inquiry findings go against Hain and forces him to quit, Brown will then be faced with appointing yet another replacement just as the consensus around the latest pension reforms is facing increased pressure over issues such as means-testing and auto-enrolment.

In the meantime, Hain has pledged to "get on with my cabinet jobs", and tomorrow the Pensions Bill Committee will hold its first evidence session on the latest reforms, with witnesses from the National Association of Pension Funds (NAPF), The Association of British Insurers (ABI) and the Investment Management Association (IMA).

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