Trade unionist; Born August 30, 1927; Died May 23, 2009.

Ken Gill, who has died aged 81, was a former general secretary of the Technical and Supervisory Section (Tass) of the Engineering Workers' Union and MSF and one of the hard-liners who gave trades unions and their leaders such high profiles in the 1960s and 1970s.

Gill was an opponent of pay restraint imposed by any government and was a critic of Margaret Thatcher. When the TUC met the Tory leader in October 1980, Gill said: "All we had from her was a primitive lecture on the evils of the trade union movement".

Eleven years earlier he led the opposition to Barbara Castle's industrial relations Bill, and in 1974 he did the same to the Wilson government's demand for a wage-restraining social contract. A member of the TUC general council, Gill was one of a broad-left group that led the ideological and battles of the 1970s.

He was born in Wiltshire and never lost his west country accent. He politics were shaped by the Depression and during the war he refused to take up officer training on ideological grounds and became an apprentice draughtsman. In the early 1950s, Gill travelled to East Germany for a youth congress and was arrested by the US military police. He was also in Paris that decade during protests demanding Algerian independence.

After some years as director of a successful small engineering firm, proving his skills as a salesman and negotiator, in 1962 Gill was elected a regional official of Data (the Draughtsmen and Allied Technicians' Association), and was posted to Liverpool. A wave of militancy swept the country, and Gill found himself leading battles over pay and conditions. His emergence as a militant, but shrewd union official led, in 1968, to him being elected deputy general secretary of the union.

At the 1968 TUC Congress, after the Soviet intervention in Czechoslovakia, he opposed calls to cut ties with Soviet trade unions, arguing that the TUC had gone on talking to American unions despite the Vietnam War. In 1970, he joined a delegation to Hanoi to show solidarity with the Viet Cong's "fight for peace".

In 1970 Data was one of three unions that combined to form the Amalgamated Union of Engineering Workers, and four years later Gill became general secretary of Data's successor, Tass. Tass left the grouping in 1985, merging after three years with the white-collar union ASTMS (the Association of Scientific, Technical & Managerial Staffs) to form MSF (the Manufacturing, Science and Finance union).

Gill was convinced that "as long as we are run by private enterprise, machines will be put in to eliminate people". Yet under his leadership Tass expanded its membership as he moved the emphasis on recruitment away from industrial draughtsmen towards technologists, computer programmers and workers in financial services.

For the first year of MSF, he led the union jointly with Clive Jenkins of ASTMS but then took control. Moderates on the MSF executive overruled him to stage a leadership election before his retirement in August 1992, and the moderate Roger Lyons succeeded him.

He was married three times: in 1953 to Jacqueline Manley, in 1967 to Tess Paterson and in 1997 to Norma Bramley.

Two sons and a daughter, all from his second marriage, survive him.