LONDON, JUNE 6 -- Iran ordered the expulsion of five British diplomats today, including Edward Chaplin, the number two man in Britain's Tehran mission who was detained and beaten by Revolutionary Guards 10 days ago.

The Iranian news agency said the move was in retaliation for Britain's "unjustified" expulsion Thursday of five diplomats assigned to the Iranian consulate in Manchester.

Although Britain had said that any Iranian retaliation would be unacceptable, officials here appeared somewhat relieved that Chaplin, described as a "criminal" yesterday by the speaker of the Iranian Parliament Ali Akbar Hashemi Rafsanjani, would be returning home.

There were fears that as long as Chaplin remained in Iran, the situation could escalate dangerously, possibly leading to a storming of the British diplomatic mission or the residential compound.

In addition, the charges against Chaplin, although never lodged formally, were said by the Iranians to include drugs, corruption and undermining the economy during wartime, which can carry the death penalty.

Since Britain closed its embassy in Iran in 1980 for security reasons, it has maintained an interests section, with 19 accredited diplomats, under the Swedish flag in Tehran. Those expelled along with Chaplin are three members of the commercial staff and a member of the chancery who also served as press spokesman.

Officials here refused to speculate on whether Britain would take action against the 19 diplomats in Iran's London embassy.

The sequence of events leading to the expulsions began last month, when one of five diplomats accredited to Iran's consulate in Manchester was arrested and charged with shoplifting. Britain rejected Iranian claims of full diplomatic immunity for the man, Ahmed Gassemi, and later accusations that Gassemi had been tortured by Manchester police.

Chaplin's abduction on May 28 was in apparent response to Gassemi's arrest. The British diplomat was taken from his car by six members of the paramilitary Revolutionary Guards and beaten when he resisted. He was released after 24 hours, but Iranian officials said they still intended to bring criminal charges against him.

Britain maintained that Chaplin was innocent of any crimes, and in any case holds full diplomatic immunity.

When Iran did not respond to Britain's demand for an apology, Foreign Secretary Geoffrey Howe ordered the Manchester consulate closed.