The Canadian government expelled 13 Soviet officials yesterday - including one-third of the Soviet embassy in Ottawa - in sweeping crackdown on Russian espionage activities.

In announcing the explusion, External Affairs Minister Don Jamieson said he had "irrefutable" evidence that the Soviets were trying to infiltrate the intelligence branch of the Royal Canadian Mounted Police.

Jamieson said the Russian were seeking information about the RCMP's counterintelligence methods and were trying to obtain character assessments of Canadian intelligence personnel.

Ottawa simultaneously lodged a strong protest with the soviet government about Russian espionage activities, which Jamieson said run "against the objective of detente and respresent a serious setback to Soviet-Canadian relations."

Jamieson, who was scheduled to pay an official visit to Moscow in March, canceled his trip. Canadian sources indicated that Soviet Foreign Trade Minister Nikolai Patolichev, due in Ottawa this month, will be asked to "postpone" his journey.

The Russians immediately cancelled the scheduled press conference today of Gen. Georgi Beregovoi, chief of the Soviet space program, who is visiting Canada.

Yesterday's crackdown was the largest Canadian security effort against Soviet espionage activities in canada since the spy roundup that followed the defection in 1945 of a cipher clerk in the Soviet embassy in Ottawa, Igor Gouzenko. His defection led to the ouster of 17 Soviet diplomats. Nine people were later convicted and nine acquitted of espionage charges.

The sweeping ouster of Soviet diplomats and the cancellation of exchange visits was expected to lead to a chill in Soviet-Canadian relations. Since his visit to Moscow in 1970, Prime Minister Pierre Trudeau has sought the cultivate better ties with the Soviet Union in pursuit of a foreign policy designed to reduce Canada's dependence on the United States.

Of the 13 expelled Soviets, 10 were members of the Soviet embassy in Ottawa, two were affiliated with the Soviet trade office, also in Ottawa, and one was employed by the International Civil Aviation Organization in Montreal. Two of the 13 had recently left Canada and were prohibited from returning. Of the remaining 11 officials, four were given 48 hours to depart and the rest will have to leave Canada before Feb. 23.

The Soviet Embassy in Ottawa employs 28 persons classified as diplomats.

Canadian officials said the ousted Soviets were part of an elaborate plot in which a Canadian security offier was offered unlimited amounts of money to spy for them.

The Canadian officer, whose name was not disclosed, fed useless information to the Soviet agents and was paid $30,500 for his efforts. According to Jamieson, the entire operation was closely monitored by Canadian security agencies.

The supplied material was "carefully screened, nonsensitive," Jamieson told parliament. "This case has involved no compromise of Canada's security."

Jamieson termed the espionage effort a "classic example of an intelligence operation - involving complex signaling systems, coded passwords, secret concealment devices, all for the purpose of arranging clandestine meetings between the RCMP member and the Soviet agent."

These activities were under surveillance between April 1977 and the present, Jamieson said. While one Soviet agent was involved in meetings with the Canadian officer, the other 12 Russians involved were engaged in support activities, he added.

The alleged main Soviet agent was identified as Igor Vartanian, listed as embassy first secretary responsible for sports and cultural affairs. The senior man involved held the rank of counselor.

There was no immediate Soviet reaction yesterday.

Canada maintains an embassy in Moscow with an active agricultural section involved in regular sales of Canadian wheat to the Soviet Union. Canadian Ambassador Robert Ford, who has been in Moscow since 1964, is the dean of the diplomatic corps.

In its official protest, the Canadian government remined Moscow that since December 1976 there were three incidents of Soviet espionage activities against Canada and that the latest incident is "a new major intelligence operation." Since Canadian diplomats in Moscow are not engaged in any kind of espionage activities against the Soviet Union, the document said, the Canadian government would regard any retaliatory action by the Russians as completely unjustified and Ottawa would retaliate in turn on the one-for-one basis.