Allegations of Mr Foot’s links to Soviet intelligence, made by double-agent Oleg Gordievsky

MI6 believed claims made by a Soviet defector that former Labour leader Michael Foot was a paid KGB contact, according to a new book.

Intelligence chiefs were reportedly briefed on the politician’s KGB history in 1982 and were prepared to pass on the information to the Queen had he become prime minister after the following year’s general election.

Allegations of Mr Foot’s links to Soviet intelligence, made by double-agent Oleg Gordievsky, were first published in the Sunday Times 23 years ago. At the time he dismissed the claims as a ‘big lie’ and successfully sued the paper for libel.

But documents, published in The Spy and the Traitor, show that MI6 thought the evidence presented by Mr Gordievsky was strong enough to pass on to the Queen.

In a 1982 debriefing, the former agent allegedly said the KGB had paid Mr Foot the equivalent of £37,000 in today’s money, according to the new book.

Even though he was supposedly paid by the Soviets, Mr Gordievsky said that the politician was not a ‘spy or conscious agent’.

Instead he was allegedly a contact who was paid for ‘disinformation purposes’, meaning he might have been fed false information.

Mr Foot lost the 1983 election to Margaret Thatcher’s Conservative Party, helped in large part by Britain’s victory in the Falklands War.

Author Ben Macintyre wrote: ‘Within MI6 there were discussions about the constitutional implications if Michael Foot won the election. It was agreed that should a politician with a KGB history become prime minister of Britain, then the Queen would have to be informed.’

The double agent (pictured) said that the Labour leader was an informant for the KGB

MI6 chiefs were so concerned about Michael Foot's (pictured, right) alleged links to the KGB that they were prepared to pass information onto the Queen (pictured, left, in 1982)

The journalist also revealed that the information was ‘too politically incendiary’ to show to Margaret Thatcher.

The allegations made against Mr Foot were detailed in a 400-page file labelled ‘Agent Boot’.

The word ‘agent’ is believed to have been later crossed out when Mr Foot was demoted to a ‘confidential contact’. The file claims Mr Foot was first contacted by Soviet intelligence while working at the left-wing magazine Tribune in the 1940s.

Mr Gordievsky also made claims about how the Soviet secret services had infiltrated other factions of the Labour Party, which had become increasingly left-wing in the early 1980s.

The party’s 1983 election manifesto, which outlined several socialist policies, was later dubbed ‘the longest suicide note in history’ by Labour MP Gerald Kaufman.

Mr Foot resigned following the election defeat and three years as Labour leader. He died in 2010 aged 96.

Trade union leader Jack Jones was also listed as an ‘agent’ by Mr Gordievsky. The spy claimed he met Mr Jones for lunch, but found him ‘absolutely useless’ as a contact.

Mr Gordievsky became a double-agent for MI6 in the 1970s, later rising to be head of the KGB’s London station in the early 1980s.