To an intelligence agency like the CIA, whose proud boast it was that, unlike the British secret services, it had never had its Philbys, Macleans and Burgesses who haemorrhaged information to the enemies of the West, the career of Philip Agee was a particular mortification.

Not that Agee literally defected to the Soviet bloc, carrying rafts of sensitive information with him, as the British traitors had done. Instead, after 12 years with the agency as an apparently highly regarded operative, he suddenly resigned in 1969 and thereafter became a resolute opponent of CIA practices. After studies which took him twice to Cuba for lengthy vists, in 1975 he published Inside the Company: CIA Diary, which contained the names and locations of hundreds of CIA agents and local organisations throughout the world.

It was an era in which the Left was enjoying unprecedented support, especially from the young, in both the US and UK after what was perceived as the moral wrong of the Vietnam War. Agee’s action did not in itself cause general outrage, in spite of the danger in which it placed many CIA agents. Indeed, the book’s publication made its author a minor celebrity, particularly among the radical young. But when, later that year, the CIA’s chief of station in Athens, Richard Welch, who had been named in a publication called Counterspy, was gunned down in front of his home, the blame was immediately laid at Agee’s door, though he denied that he had given Welch’s name to Counterspy.

He was subsequently accused in the US Congress of having identified the Polish Olympic fencer Jerzy Pawlowski to the Soviet Union as a Western agent. In 1976 Pawlowlski was sentenced to 25 years in jail on charges of spying for the CIA. Altogether the damage wrought by Agee’s revelations in the immediate term was enormous. As the years went by his power to annoy the American security apparatus became progressively weaker. But he remained a thorn in the side to the US and, in particular, a permanent blot on the CIA escutcheon.

Philip Burnett Franklin Agee was born in 1935 in Tacoma Park, Florida, and educated at the University of Notre Dame, from where he graduated in 1956. The following year he was recruited by the CIA for whom he worked as a case officer first in Washington, and then in Ecuador, Uruguay and Mexico.

But his experience of how the agency operated in its support of right-wing governments across Central and South America began, he claimed, to give him serious unease. In Ecuador one of his first important missions was to engineer a diplomatic rift between Cuba and Ecuador, something that was achieved at huge cost to Ecuador’s febrile stability. The means of achieving this were bribery, intimidation of officials, bugging and the use of forged documents and letters. In his opinion his actions and those of his colleagues had destroyed the political fabric of the country and prevented any chance of its evolving healthily.

A moment of truth, he was later to say, was a visit in 1965 to Uruguayan military and police contacts at the police headquarters in Montevideo. He was told with gratitude that the screams of someone being tortured in the next room were those of a suspect whose name he had shortly before given them merely as “someone to watch”. When he expressed horror senior police officers simply turned up the report of soccer match being broadcast on a radio in the room to drown out the man’s screams.

From Uruguay he went to Mexico where the CIA ran operations within the 1968 Olympic Games. It was while on station there that he resigned in January 1969, citing “personal reasons” at the time, later revised to an objection to the CIA’s support for “the corruption, ineffectiveness and greed among the traditional political forces that we were supporting”. This view was to be challenged by John Barron, who in his book KGB Today: The Hidden Hand, published in 1983, claimed that the reason Agee was released from the CIA was “irresponsible drinking, continuous and vulgar propositioning of embassy wives, and inability to manage his finances”.

On leaving the CIA Agee embarked on a postgraduate course of Latin American studies at the National Autonomous University of Mexico. But a book about his CIA career was already germinating, its mission: “to show the hypocritical, corrupt and self-defeating nature of the CIA’s clandestine intervention to subvert institutions of friend and potential foe alike”.

According to the KGB’s chief archivist Vassili Mitrokhin (obituary January 29, 2004), co-author with Christopher Andrew of The Mitrokhin Archive: The KGB in Europe and the West, a number of Soviet defectors claimed that in 1973 Agee offered the KGB’s resident in Mexico City a mine of valuable infomation, but the resident turned it down. The former head of the KGB’s counterintelligence division, Oleg Kalugin, subsequently went on record as saying: “I cursed our officers for turning away such a prize”.

In any event, Agee did not collaborate with the Soviet Union, but his research took him to Cuba, where he was welcomed. A house and two student researchers were put at his disposal. The CIA became convinced that he had in fact been recruited by the Cuban secret service, itself a localised branch of the KGB.

Agee stayed in Cuba for six months, subsequently basing himself in Paris to finish his book, though he did pay further visits to Cuba. The publication of Inside the Company was a sensation, not so much for its revelations about the state of CIA current operations — time had elapsed since Agee’s service, and a certain amount of damage limitation had between possible. The publication of the names of large numbers of CIA operatives was another matter and many active careers had to be terminated by the agency, for the sake of the individuals named.

Unrepentant, Agee continued to publish names and even addresses of agents, and many of these were named in Counterspy. While Agee denied “fingering” the unfortunate Welch in this publication, he was on record in its columns as asserting: “The most effective and important systematic attempts to combat the CIA that can be undertaken right now are, I think, the identification, exposure, and neutralisation of its people working abroad”. To the CIA such an exhortation led inescapably to the death of Welch. Britain’s Secret Intelligence Service (MI6) also blamed Agee, by then based in London, for the murder of two of its agents in Poland.

The US demanded that Agee be deported from the UK. During 1976 he was at the centre of a campaign by dozens of left-wing MPs, journalists and others, to resist this pressure, a campaign in which he was associated with the American journalist Mark Hosenball, whom the US Government also wanted expelled for similar reasons. An Agee-Hosenball Defence Committe was established, with the support of a number of respected names on the radical Left, but in the end to no avail.

In 1977 he left the UK for the Netherlands. He was for some time peripatetic, being expelled from most Western European countries, en route to being given periods of harbourage in Grenada (curtailed by the collapse of its revolution), Nicaragua (again terminated by regime change) and Cuba. With his second wife, the German ballet dancer Giselle Roberge, he subsequently lived in Germany and Cuba.

He continued to publish: Dirty Work: The CIA in Western Europe (1978) and Dirty Work: The CIA in Africa (1979) contained the names of several thousand CIA agents. His autobiography On the Run was published in 1987. Latterly he had spent more time in Cuba where he died in hospital, having undergone surgical treatment for perforated ulcers.

He is survived by his wife and the two sons of his first marriage.

Philip Agee, CIA agent and author, was born on July 19, 1935. He died on January 7, 2008, aged 72