For decades in art circles it was either a rumour or a joke, but now it is confirmed as a fact. The Central Intelligence Agency used American modern art - including the works of such artists as Jackson Pollock, Robert Motherwell, Willem de Kooning and Mark Rothko - as a weapon in the Cold War. In the manner of a Renaissance prince - except that it acted secretly - the CIA fostered and promoted American Abstract Expressionist painting around the world for more than 20 years.

The connection is improbable. This was a period, in the 1950s and 1960s, when the great majority of Americans disliked or even despised modern art - President Truman summed up the popular view when he said: "If that's art, then I'm a Hottentot." As for the artists themselves, many were ex- communists barely acceptable in the America of the McCarthyite era, and certainly not the sort of people normally likely to receive US government backing.

Why did the CIA support them? Because in the propaganda war with the Soviet Union, this new artistic movement could be held up as proof of the creativity, the intellectual freedom, and the cultural power of the US. Russian art, strapped into the communist ideological straitjacket, could not compete.

Download the new Independent Premium app Sharing the full story, not just the headlines

The existence of this policy, rumoured and disputed for many years, has now been confirmed for the first time by former CIA officials. Unknown to the artists, the new American art was secretly promoted under a policy known as the "long leash" - arrangements similar in some ways to the indirect CIA backing of the journal Encounter, edited by Stephen Spender.

The decision to include culture and art in the US Cold War arsenal was taken as soon as the CIA was founded in 1947. Dismayed at the appeal communism still had for many intellectuals and artists in the West, the new agency set up a division, the Propaganda Assets Inventory, which at its peak could influence more than 800 newspapers, magazines and public information organisations. They joked that it was like a Wurlitzer jukebox: when the CIA pushed a button it could hear whatever tune it wanted playing across the world.

The next key step came in 1950, when the International Organisations Division (IOD) was set up under Tom Braden. It was this office which subsidised the animated version of George Orwell's Animal Farm, which sponsored American jazz artists, opera recitals, the Boston Symphony Orchestra's international touring programme. Its agents were placed in the film industry, in publishing houses, even as travel writers for the celebrated Fodor guides. And, we now know, it promoted America's anarchic avant-garde movement, Abstract Expressionism.

Initially, more open attempts were made to support the new American art. In 1947 the State Department organised and paid for a touring international exhibition entitled "Advancing American Art", with the aim of rebutting Soviet suggestions that America was a cultural desert. But the show caused outrage at home, prompting Truman to make his Hottentot remark and one bitter congressman to declare: "I am just a dumb American who pays taxes for this kind of trash." The tour had to be cancelled.

The US government now faced a dilemma. This philistinism, combined with Joseph McCarthy's hysterical denunciations of all that was avant-garde or unorthodox, was deeply embarrassing. It discredited the idea that America was a sophisticated, culturally rich democracy. It also prevented the US government from consolidating the shift in cultural supremacy from Paris to New York since the 1930s. To resolve this dilemma, the CIA was brought in.

The connection is not quite as odd as it might appear. At this time the new agency, staffed mainly by Yale and Harvard graduates, many of whom collected art and wrote novels in their spare time, was a haven of liberalism when compared with a political world dominated by McCarthy or with J Edgar Hoover's FBI. If any official institution was in a position to celebrate the collection of Leninists, Trotskyites and heavy drinkers that made up the New York School, it was the CIA.

Until now there has been no first-hand evidence to prove that this connection was made, but for the first time a former case officer, Donald Jameson, has broken the silence. Yes, he says, the agency saw Abstract Expressionism as an opportunity, and yes, it ran with it.

Daily coronavirus briefing No hype, just the advice and analysis you need Enter your email address Continue Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid Email already exists. Log in to update your newsletter preferences Register with your social account or click here to log in I would like to receive morning headlines Monday - Friday plus breaking news alerts by email Update newsletter preferences

"Regarding Abstract Expressionism, I'd love to be able to say that the CIA invented it just to see what happens in New York and downtown SoHo tomorrow!" he joked. "But I think that what we did really was to recognise the difference. It was recognised that Abstract Expression- ism was the kind of art that made Socialist Realism look even more stylised and more rigid and confined than it was. And that relationship was exploited in some of the exhibitions.

"In a way our understanding was helped because Moscow in those days was very vicious in its denunciation of any kind of non-conformity to its own very rigid patterns. And so one could quite adequately and accurately reason that anything they criticised that much and that heavy- handedly was worth support one way or another."

To pursue its underground interest in America's lefty avant-garde, the CIA had to be sure its patronage could not be discovered. "Matters of this sort could only have been done at two or three removes," Mr Jameson explained, "so that there wouldn't be any question of having to clear Jackson Pollock, for example, or do anything that would involve these people in the organisation. And it couldn't have been any closer, because most of them were people who had very little respect for the government, in particular, and certainly none for the CIA. If you had to use people who considered themselves one way or another to be closer to Moscow than to Washington, well, so much the better perhaps."

This was the "long leash". The centrepiece of the CIA campaign became the Congress for Cultural Freedom, a vast jamboree of intellectuals, writers, historians, poets, and artists which was set up with CIA funds in 1950 and run by a CIA agent. It was the beach-head from which culture could be defended against the attacks of Moscow and its "fellow travellers" in the West. At its height, it had offices in 35 countries and published more than two dozen magazines, including Encounter.

The Congress for Cultural Freedom also gave the CIA the ideal front to promote its covert interest in Abstract Expressionism. It would be the official sponsor of touring exhibitions; its magazines would provide useful platforms for critics favourable to the new American painting; and no one, the artists included, would be any the wiser.

This organisation put together several exhibitions of Abstract Expressionism during the 1950s. One of the most significant, "The New American Painting", visited every big European city in 1958-59. Other influential shows included "Modern Art in the United States" (1955) and "Masterpieces of the Twentieth Century" (1952).

Because Abstract Expressionism was expensive to move around and exhibit, millionaires and museums were called into play. Pre-eminent among these was Nelson Rockefeller, whose mother had co-founded the Museum of Modern Art in New York. As president of what he called "Mummy's museum", Rockefeller was one of the biggest backers of Abstract Expressionism (which he called "free enterprise painting"). His museum was contracted to the Congress for Cultural Freedom to organise and curate most of its important art shows.

The museum was also linked to the CIA by several other bridges. William Paley, the president of CBS broadcasting and a founding father of the CIA, sat on the members' board of the museum's International Programme. John Hay Whitney, who had served in the agency's wartime predecessor, the OSS, was its chairman. And Tom Braden, first chief of the CIA's International Organisations Division, was executive secretary of the museum in 1949.

Now in his eighties, Mr Braden lives in Woodbridge, Virginia, in a house packed with Abstract Expressionist works and guarded by enormous Alsatians. He explained the purpose of the IOD.

"We wanted to unite all the people who were writers, who were musicians, who were artists, to demonstrate that the West and the United States was devoted to freedom of expression and to intellectual achievement, without any rigid barriers as to what you must write, and what you must say, and what you must do, and what you must paint, which was what was going on in the Soviet Union. I think it was the most important division that the agency had, and I think that it played an enormous role in the Cold War."

He confirmed that his division had acted secretly because of the public hostility to the avant-garde: "It was very difficult to get Congress to go along with some of the things we wanted to do - send art abroad, send symphonies abroad, publish magazines abroad. That's one of the reasons it had to be done covertly. It had to be a secret. In order to encourage openness we had to be secret."

If this meant playing pope to this century's Michelangelos, well, all the better: "It takes a pope or somebody with a lot of money to recognise art and to support it," Mr Braden said. "And after many centuries people say, 'Oh look! the Sistine Chapel, the most beautiful creation on Earth!' It's a problem that civilisation has faced ever since the first artist and the first millionaire or pope who supported him. And yet if it hadn't been for the multi-millionaires or the popes, we wouldn't have had the art."

Would Abstract Expressionism have been the dominant art movement of the post-war years without this patronage? The answer is probably yes. Equally, it would be wrong to suggest that when you look at an Abstract Expressionist painting you are being duped by the CIA.

But look where this art ended up: in the marble halls of banks, in airports, in city halls, boardrooms and great galleries. For the Cold Warriors who promoted them, these paintings were a logo, a signature for their culture and system which they wanted to display everywhere that counted. They succeeded.

* The full story of the CIA and modern art is told in 'Hidden Hands' on Channel 4 next Sunday at 8pm. The first programme in the series is screened tonight. Frances Stonor Saunders is writing a book on the cultural Cold War.

Covert Operation

In 1958 the touring exhibition "The New American Painting", including works by Pollock, de Kooning, Motherwell and others, was on show in Paris. The Tate Gallery was keen to have it next, but could not afford to bring it over. Late in the day, an American millionaire and art lover, Julius Fleischmann, stepped in with the cash and the show was brought to London.

The money that Fleischmann provided, however, was not his but the CIA's. It came through a body called the Farfield Foundation, of which Fleischmann was president, but far from being a millionaire's charitable arm, the foundation was a secret conduit for CIA funds.

So, unknown to the Tate, the public or the artists, the exhibition was transferred to London at American taxpayers' expense to serve subtle Cold War propaganda purposes. A former CIA man, Tom Braden, described how such conduits as the Farfield Foundation were set up. "We would go to somebody in New York who was a well-known rich person and we would say, 'We want to set up a foundation.' We would tell him what we were trying to do and pledge him to secrecy, and he would say, 'Of course I'll do it,' and then you would publish a letterhead and his name would be on it and there would be a foundation. It was really a pretty simple device."

Julius Fleischmann was well placed for such a role. He sat on the board of the International Programme of the Museum of Modern Art in New York - as did several powerful figures close to the CIA.