The Soviet government expelled a British diplomat and a journalist today in retaliation for the ouster from London last week of two Soviet diplomats and one correspondent.

Squadron Leader David Williams, an assistant air attache at the British Embassy here, and Anthony Robinson, Moscow correspondent of the Financial Times, were given a week to leave.

Soviet authorities were also considering possible retaliatory actions against France, which ordered out 47 Soviet diplomats, journalists and officials earlier this week.

There was a distinct prospect that the expulsions and retaliations could escalate and bring about a further deterioration in East-West relations.

Following the ouster of a Soviet military attache, a second secretary of the Soviet Embassy in London and the correspondent of the Soviet weekly New Times last week, British officials warned Moscow that Prime Minister Margaret Thatcher's government would order still more Soviet officials out of Britain if Moscow took retaliatory steps.

A British Embassy spokesman declined comment on possible new retaliatory steps by London.

A senior Soviet official said the expulsions ordered by the French and British are seen here as a part of a "political and propaganda campaign orchestrated by the Reagan administration to discredit" Moscow's foreign policy. He predicted that "these hysterical things will be short-lived" and that Moscow would be "restrained" in its response.

Sir Iain Sutherland, the British ambassador, "protested strongly at this totally unjustified action," the British spokesman said. "This action is clearly in retaliation for the expulsion of three Soviet officials from London last week."

British officials said Vladimir Suslov, a senior Foreign Ministry official who read the expulsion order to the British ambassador, did not elaborate on the charge that Williams and Robinson were involved in "impermissible activities."

Williams, 33, has been here less than a year. The last British diplomat to be expelled by the Soviets was Capt. Bruce Richardson, the naval attache, who was ousted last December after Britain's expulsion of the Soviet naval attache.

Correspondent Robinson, 40, is highly regarded in the foreign community here. He arrived a year ago. The last British correspondent expelled was David Bonavia of the London Times in 1972.