WILLIAM HAGUE was dragged to the centre of the Lord Ashcroft scandal yesterday when he admitted he knew of the billionaire donor’s non-dom status some months ago.

The Richmond MP and Shadow Foreign Secretary became the first Conservative to acknowledge he knew the truth about the peer’s tax status – piling pressure on leader David Cameron to answer the same question.

Mr Hague also faced embarrassment over the release of letters, sent to the then Prime Minister Tony Blair in 1999, in which he said Lord Ashcroft was “committed to becoming resident” for tax purposes.

In a private letter, insisting the peerage should be granted, Mr Hague wrote: “This decision will cost him (and benefit the Treasury) tens of millions a year in tax, yet he considers it worthwhile.”

On Monday, Lord Ashcroft stunned many Tories by admitting he was still a nondom, thus avoiding tax estimated at £12m a year on his worldwide income – despite receiving his seat in the Lords.

Facing Mr Hague in the Commons, Labour’s deputy leader, Harriet Harman, argued it was impossible for both Mr Hague and the billionaire peer to be correct in their statements about the promises made.

She said: “The Shadow Foreign Secretary stands here without a shred of credibility.”

Insisting they could not “both be right”, she added: “One of them must go.”

The deputy leader, standing in for Gordon Brown, also taunted Mr Hague that Lord Ashcroft, when discussing his peerage in his autobiography, had written: “I owe it all to William.”

But Mr Hague hit back, telling MPs the real scandal in British political funding was the bankrolling of the Labour Party by the Unite union.

He said: “People in glass houses should not start throwing stones. I think we know what a desperate panic the Government are in.”

Mr Hague’s letter followed the political honours committee’s 1999 refusal of Lord Ashcroft’s nomination for a peerage. In it, he acknowledged that one reason for its decision was that “Mr Ashcroft was a tax exile”.

Last night, in an interview with the BBC, Mr Hague admitted knowing Lord Ashcroft was still a non-dom before Monday’s statement, adding: “Over the last few months I knew about that.”

In contrast, Mr Cameron, in earlier interviews, refused to answer further questions, saying: “They have been answered.

So as far as I am concerned, this issue has now been sorted.”

But Labour – which is furious that Lord Ashcroft has pumped millions of pounds into Tory campaigns in marginal seats – scented blood.

Douglas Alexander, its General Election co-ordinator, said: “It is clear tonight that neither David Cameron nor William Hague have sought the reassurances from Michael Ashcroft that they needed to.

“They have been content to take his hard cash, while apparently not asking the hard questions.

“They should now return the money Lord Ashcroft has given the Conservative Party, since he took his peerage, to the British taxpayer.”