The diplomats made the secret approach through Mr Aziz’s lawyer this week on behalf of Parliament’s so-called “sleaze buster”. The lawyer, Badie Izzat Arief, claimed that they offered to try and secure Mr Aziz immunity from prosecution on any charges arising from the Oil-for-Food scandal.

Embassy officials want to meet Mr Aziz, 70, in the US-run detention centre where he is held with other top members of Saddam’s regime to put a series of questions from Sir Philip Mawer, the Parliamentary Commissioner for Standards.

Sir Philip is investigating claims that the MP for Bethnal Green & Bow took money under the UN Oil-for-Food programme — a charge that Mr Galloway strenuously denies and about which he has already successfully sued and won damages from one national newspaper.

Mr Arief told The Times that his client has been interrogated 312 times by the CIA and UN investigators since his arrest in April 2003, but this was the first British approach.“We were surprised to hear from the British, but let’s see what they want,” Mr Arief said.

“The main question I believe is whether money was paid by anyone in Iraq to Mr Galloway’s charity, the Mariam Appeal.”

He said that US officials had asked his client more than 100 detailed questions about Western politicians alleged to have received money from Saddam, but none about Mr Galloway.

“The CIA haven’t asked about Mr Galloway. They are obsessed with Jacques Chirac. Mr Aziz told them: ‘I find it strange you want revenge on Chirac. He is the respected President of France, so I regard the question as insulting.’ ”

Mr Aziz, who also served as Saddam’s Foreign Minister, spent a Christmas holiday with Mr Galloway, in Baghdad, in 1999. Mr Galloway described him as “an eminent diplomat and intellectual person”.

In the same interview Mr Arief said that Mr Aziz, who surrendered to US forces soon after the 2003 invasion and has never been charged, is suffering from deteriorating health.

He revealed how Saddam’s former right-hand man now lives in a small cell in what was a Republican Guard barracks, now part of Camp Cropper, the huge US base near Baghdad airport.

The urbane, English-speaking envoy with a passion for handstitched suits now shuffles about in a tatty tracksuit and flip-flops in his 6ft by 5ft cell, with just a narrow bed, a hardback chair and a small cupboard for furniture.

“He is a shrunken figure,” Mr Arief said. “He can’t walk unaided, doesn’t eat properly and isn’t taking care of himself. The Americans are keeping him in the hope of browbeating him into testifying against Saddam. As a matter of conscience, he won’t,” Mr Arief said.

George Galloway said last night that it was “very significant” that Britain had approached Mr Aziz to seek information about him before next week’s local elections, in which his Respect Party is expected to take seats from Labour. Mr Galloway said: “I could question the propriety of visiting a political prisoner who has had heart attacks and strokes and who is being systematically denied family visits, medical visits and legal visits.”

He added: “But I have every confidence that Mr Aziz will have told them that there is no truth whatsoever in these persistent allegations.”

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