WILLIAM COLBY, who has died aged 76, was director of the United States Central Intelligence Agency from 1973 to 1976.

Slim, with blue eyes and slicked-back hair, Colby was likeable, low-key and almost deliberately anti-charismatic. Edward Kennedy described him as "the epitome of the covert man". Having worked his way up the CIA almost from its foundation in 1947, Colby knew what he was talking about when he described a real spy as "a grey man who has a hard time catching the eye of a waiter in a restaurant".

Yet as head of the directorate of operations - known as the Department of Dirty Tricks - he was in charge of all the agency's covert intelligence-gathering work and its secret political operations.

Colby's time as director spanned one of the most difficult periods in the agency's history. He took office in the last year of President Nixon's administration, when Vietnam and Watergate had divided America and weakened the presidency, spawning an aggressive suspicion both of official secrecy and foreign involvements.

From the moment Colby became director he faced pressure to shed light on the agency's activities. He declared - as his two predecessors had done before him - that it was his intention to scale down the clandestine operations of the CIA.

After the fall of Nixon in 1974 the CIA came under the scrutiny of a new breed of inquisitor in the media and on Capitol Hill. Colby had to decide whether to guard the agency's secrets still more closely, or to disclose a fuller record, in the hope of rebutting the wilder charges.

He decided on openness. Soon after his appointment he told the Senate Armed Services Committee that the CIA had no business in domestic intelligence. Chipping away at what he claimed was the agency's preoccupation with secrecy, he allowed reporters and television crews unprecedented tours of the agency's headquarters at Langley, Virginia. He even had a sign reading "CIA" installed on the access road.

In April 1974 Colby testified before a House subcommittee about the agency's involvement in Chile during the period preceding the coup that toppled Allende in September 1973

In April 1974 Colby testified before a House subcommittee about the agency's involvement in Chile during the period preceding the coup that toppled Allende in September 1973.

His revelations forced President Ford to confirm that from 1970 to 1973 his predecessor's administration had authorised the spending of more than $8 million to destabilise Allende's government. Colby insisted that the CIA had not been responsible for the coup against the Chilean leader; nevertheless he had admitted enough to touch off a new debate about the CIA's secret political operations.

In 1975 several House committees and Vice-President Nelson Rockefeller's special commission looked into allegations of illegal domestic spying, CIA experimentation with the drug LSD, and illegal electronic eavesdropping.

His urge to put the record straight earned him the ire of President Ford, who felt that CIA secrets were the property of the Executive, and not for the prurient hacks in Congress - least of all at election time

Doubts about the policy of openness began to proliferate in government circles. "Bill, you know what you do when you go up to the Hill [Congress]?" Henry Kissinger demanded of the Roman Catholic Colby. "You go to Confession." Rockefeller, too, wondered tactfully, in a private conversation with Colby, whether it was really necessary to present "all this material to us".

But Colby saw it as a matter of conscience to co-operate with Congress, whatever the cost. His urge to put the record straight earned him the ire of President Ford, who felt that CIA secrets were the property of the Executive, and not for the prurient hacks in Congress - least of all at election time.

Finally, in November 1975, Ford announced that Colby would be replaced as director by George Bush, then serving as a diplomat in Peking.

William Egan Colby was born on Jan 4 1920 in St Paul, Minnesota, the son of an army officer, and was brought up in a series of army posts. From Burlington High School, Vermont, he went on to Princeton, from which he graduated in 1940. After a year at Columbia Law School he left to join the army as a staff lieutenant with the 462d Parachute Artillery Battalion.

He later joined the Office of Strategic Services, America's wartime intelligence agency concerned with undercover activities, and in August 1944 he parachuted into north-central France to link up with a Resistance group.

After the war, Colby returned to Columbia to gain his law degree and then joined a New York law firm which had been founded by William J Donovan, formerly commander of the Office of Strategic Services

After the war, Colby returned to Columbia to gain his law degree and then joined a New York law firm which had been founded by William J Donovan, formerly commander of the Office of Strategic Services. On the outbreak of the Korean war in 1950 he left to join the CIA, which had been set up three years earlier to co-ordinate the intelligence activities of the various government departments.

In 1951 Colby was sent under diplomatic cover to the American embassy in Stockholm; in 1953 he became first secretary and special assistant to the ambassador in Rome. In 1959 he was appointed first secretary of the American embassy in Saigon, where he headed the CIA operations as station chief. Although he left Saigon in 1962, Colby remained closely connected to Vietnamese affairs as chief of the Far East division of the plans directorate. When President Johnson sent Robert Komer, a White House special assistant, to Saigon as head of Civil Operations and Rural Development Support (Cords), the Vietnamese pacification programme, Colby - though previously earmarked for the top CIA job in Moscow - was sent to join him.

Many considered that Phoenix had been a brutal and unjustifiable operation in which the intelligence services ran out of control

Some of these initiatives concerned only road building and health care. But they also entailed Operation Phoenix, which was designed to weed out Vietcong agents. Under Colby's direction, 28,978 suspected Vietcong were captured or jailed, 17,717 were persuaded to defect, and 20,587 were killed.

Many considered that Phoenix had been a brutal and unjustifiable operation in which the intelligence services ran out of control. One former intelligence agent told a House subcommittee that some captured Vietcong suspects were interrogated in helicopters, and that the lesser fry were pushed out to persuade more important suspects to talk. Still more chilling methods of torture were practised on the ground.

Colby later denied that Phoenix had been a counter-terror programme, but admitted that there might have been "some illegal killing" and "some unjustifiable abuses".

He returned to the United States in 1971, the next year became executive director-controller of the CIA, and in March 1973 was promoted deputy director for operations. A month later Nixon appointed the CIA director James Schlesinger Secretary of Defense, and Colby as his successor.

After leaving the CIA Colby returned to the law in Washington. In interviews which he gave in 1978, when his autobiography, Honourable Men - My Life in the CIA, was published, he called for a new law to punish breaches of security by former members of the CIA.

William Colby married, in 1945, Barbara Heinzen; they had five children.

Reply to Electronic Telegraph

Electronic Telegraph is a Registered Service Mark of The Telegraph plc