The young Rowan Williams was once labelled 'a subversive' by a senior MI5 officer over his involvement with a group of Marxist, Trotskyite and socialist campaigners.

The secret briefing papers were seen by then Prime Minister Baroness Thatcher and circulated to MPs.

Last week Dr Williams, who describes himself as a "lapsed" Labour party member held private talks with Ed Miliband, the leader of the opposition, in the wake of his New Statemsman article which attacked the coalition.

The future head of the Church of England first came to the attention of the Security Service when he helped found a left-wing Christian group during his student days at Oxford University.

He wrote the original manifesto for the Jubilee Group, claiming capitalism was in its death-throes and 'threatens to inflict even greater violence on manking than it has done before'.

Rubbing shoulders with left-wing politicians such as Tony Benn and the late Eric Heffer, he wrote: 'We must make our stand with the oppressed'.

The Jubilee Group was identified as a "problem" neo-Marxist organisation in confidential intelligence documents drawn up by MI5 officer Charles Elwell.

He warned of "the problem of Christian left wing groups" and named the Jubilee Group as "the best known and probably most influential".

Mr Elwell, who died in 2008, spent much of his career investigating left of centre politicians, charity workers and trade unionists, first in MI5's now defunct counter-subversion F branch and then privately for the shadowy Institute for the Study of Conflict, which was allegedly part funded by the CIA and MI6.

He delivered his warning warned about Dr Williams' group in 1989 in the privately-funded British Briefing, a newsletter circulated to a secret list of politicians, including Baroness Thatcher, and selected journalists.

Shortly after its analysis of Dr Williams' group was published, the Prime Minister said the Jubilee Group was "the most subversive group within the religious community in England" and one newspaper referred to it as "a bunch of neo-Marxist trendy clerics."

The group helped oversee a series of campaigns against the introduction of the poll tax, the violent trade union dispute over Rupert Murdoch's decision to move his newspapers to Wapping and the US nuclear base at Greenham Common.

The group also condemned Baroness Thatcher's views on immigration. When she said she feared Britain would be "swamped by people of a different culture", the Jubilee Group accused the Tories of "racism and creeping fascism", adding: "It is a phenomenon which is far more dangerous than that of the National Front".

Dr Williams was a leading member of the radical Jubilee Group's executive committee during the 1970s and 1980s alongside Mr Heffer, Mr Benn and Communist priest Rev Alan Ecclestone.

The archbishop, an Oxford graduate, was ordained a priest in 1977 but spent almost all of his clerical career until he was consecrated a bishop in 1991 as a lecturer at Cambridge and Oxford universities.

In 1974, he had co-written a manifesto for the group with his friend John Saward, now a Catholic priest, in the Horse and Jockey pub on Woodstock Road, Oxford. They claimed: "We are "subversive contemplatives". We are not shallow activists."

Their manifesto railed against "the ruthless pursuit of private gain" and the "idolatry of profit" adding: "We cannot...feign neutrality, or remain uncritical, in the face of a society based upon the ruthless pursuit of private gain and unlimited consumption."

It concluded: "We do not run away from history. We know what the present crisis of capitalism demands of us...we are in the death-throes of late capitalism, which threatens to inflict even greater violence on mankind than it has done before, we must make our stand with the oppressed, with the movement for liberation throughout the world."

According Rev Dr Ken Leech, the group's founder member, the manifesto was never formally adopted. He said: "It reflected our thinking at the time, but the view was it was too much of a rant. It was a fascinating document, but rather triumphalist, and we rejected it."

He added: "At the time we had never heard of Rowan Williams. He was introduced to us by John Saward. But he became very involved, regularly attended meetings, running our literature committee, giving lectures and writing pamphlets."

Together they edited a series of essays "Catholic and Radical" for the group, and the Rev Dr Leech is still in regular touch with the Archbishop who hosted a 70th birthday party for him at Lambeth Palace last year.

He added: "I would not want to commit Rowan to the language of 1974...but it does really show the heart of the theological focus of the man and this has not changed."

The group's actions were planned in a Notting Hill flat in west London where the young Dr Williams would turn up early to learn traditional pasta-making skills from Margaret Ronchetti, who hosted the meetings.

From the flat and also at the Hoop and Grapes pub in Aldgate, in the City of London, the Jubilee Group bitterly attacked Margaret Thatcher's government over the Falklands War, her policy towards the trade unions and nuclear weapons.

It campaigned against the controversial poll tax.

"We must fight this evil tax" the group's May 1989 newsletter said.

During this period Dr Williams was arrested for "singing Psalms" at a CND demonstration outside RAF Lakenheath, a nuclear weapons base in Suffolk, and questioned Baroness Thatcher's references to her religious convictions to back her political views.

In a speech at Edinburgh University in 1989 he talked of "the alarming religiosity of Ronald Reagan (then US President) and Margaret Thatcher."

Detals of confidential briefing from Mr Elwell, nicknamed the 'MI5's Witchfinder General', were uncovered by a Canadian PhD student researching Rowan williams and the Church's left-wing traditions.

Mr Elwell was himself a controversial figure, best known for exposing the 'Portland spy ring', which identified a Royal Navy traitor passing secrets to the Soviets.

A note in each issue of the British Briefing asked readers 'to refrain from mentioning it, or its existence, or from direct quotation'. Its contents were believed to have been approved at a high level in the Security Service.

The briefings were seen as a "dirty tricks" campaign against the so-called "enemy within". Patricia Hewitt and Harriet Harman, both later Labour cabinet ministers, were also targetted when they were general secretary and legal officer of the National Council for Civil Liberties (now Liberty) in the 1970s.

The Briefings were also funded by David Hart, an adviser to Baroness Thatcher and to National Coal Board boss Ian MacGregor during the miners' strike in 1984. Hart, who died earlier this year, founded the Committee for a Free Britain, a right wing pressure group.

(Additional reporting: Rebecca Lefort, Edward Malnick and Alan Rimmer)