Tens of thousands of civil servants in government offices, ports and prisons went on strike Monday to protest the firing of union workers at Britain's intelligence-gathering headquarters.

A spokesman for the Council of Civil Service Unions, an umbrella body for Britain's eight civil service unions, estimated 200,000 workers took part in the one-day walkout.Dozens of lunchtime rallies were held to protest the recent firings of five men at the Government Communications Headquarters in Cheltenham. The huge southwest England facility eavesdrops on the Soviet Union, and the government maintains its work is too sensitive to risk disruption by strikes.

The firings provoked new charges that Prime Minister Margaret Thatcher's government is undermining civil liberties.