The defection to Britain of a Czechoslovak intelligence officer who had worked under cover here as a journalist for six years is being viewed as a potentially important catch for Western counterspy operations.

According to imnformed sources, Czechoslovakia is surpassed only by East European countries in its intelligence gathering in West Germany.

[In Ottawa, Canada announced that it will expel a Soviet exchange scientist on suspicion of espionage].

The Czechoslovak defector is identified as Svetozar Simko, 36, the former chief of the Bonn bureau of the official Czechoslovak news agency CTK.

Czechoslovak spying here is believed to be quite active and there is speculation that Simko's defection could blow the cover off a large operation.

According to the London Daily Telegraph which reported the defection today, which reported the defection today, Simko has already labeled 17 out of 27 diplomats in the Czechoslovak embassy here as connected with the spy network.

He also named officials, Rudolf Koval and Valadimir Krulich, as head of the civilian and military intelligence services in West Germany. Sources say they have no reason to doubt the claims.

THe West German counterespionage service in Cologne confirmed today that it had been aware of Simko's spy work for some time, as did other Western sources.

Informants suggest that experienced spy-journalists often are among the most valued agents for Eastern countries because they generally have wider range of informal contacts than most diplomats.

Journalist-spies often are believed to have a better feel for their own country's overall intelligence objectives than higher level, covert spies who may work only on specific projects.

According to the initial Daily Telegraph report, Simko also told authorities of various radio transmitters, mini-cameras and stockpiles of cash hidden in the West German hills by Eastern agents for use of saboteurs in wartime.

Other sources tended to view such descriptions as probably accurate but over-dramatized. Informants said that the Czechoslovaks migh have done this but coordination among agents from other Communist countries is generally viewed as not very effective.

Although West Germany traditionally has been a magnet for Communist spies - with estimates that perphaps 8,000 operate here - West German counterintellignce is credited with considerable gains in tracking them down in recent years.

East Germans are said to run about 60 per cent of the Communist activities here, but Western sources estimate that only a tiny fraction of agents could or would get involved in actual sabotage iunder wartime conditions.

Simko's predecessor here for CTK, Otakar Svercina, also West Germans raided his apartment six years ago. The raiders apparently did not turn up enough to make a case.

After a protest from the foreign correspondent's association here, a government spokesman made a public apology and a bouquet of flowers was sent to Svercina's home.

Simko is not the fisrt Czechoslovak agent to defect to Britain, which has a large exile community. Several years ago two other defected and provided information that led to the identification of some 100 Czechoslovak agents in Britain.

The Dally Telegraph described Simko as an "Anglophile" who always wanted to move his family to the West. Other sources say this affinity for Britain does seem to exist among a number of Czechoslovaks who operate in the West.

The Bonns government today said it was examining the claims made by Simko in London before deciding what, if anything, to do. The Czechoslovak embassy said it would have no comment.