LONDON, JUNE 10 -- Britain today ordered Iran to reduce its diplomatic presence here by two in the latest of a series of expulsions between the two countries.

Last month, Britain ordered Iran to close its five-man consulate in Manchester after a British diplomat was abducted and beaten in Tehran late last month. Iran responded last week by expelling five British envoys.

A Foreign Office statement said today a new "ceiling" of 16 had been placed on the Iranian Embassy in London, where 18 staffers are presently working. Britain said it also "expected full cooperation from the Iranian authorities" in restoring its own diplomatic mission in Tehran from the current 14 envoys to an equivalent level of 16.

The Foreign Office statement said that the new "principle of strict numerical reciprocity" would take effect on June 24.

Although government officials here said they hoped that this latest retaliation would end the controversy, they showed little optimism.

Other western diplomats, however, said they doubted that Iran wanted to sever relations. In addition to its embassy here, Tehran also operates a large office in London. A facility of the National Iranian Oil Co., the office serves as its main overseas agency for international arms purchases.