The British government has decided "to advise British athletes not to go to Moscow" for next summer's Olympic Games, Prime Minister Margaret Thatcher told Parliament today.

This moves Britain's public position beyond Thatcher's previous campaign in support of President Carter to have the International Olympic Committee move or postpone the Moscow games. It refused to take that step Tuesday at its meeting in Lake Placid, N.Y.

Asking athletes to stay home may be the most that Britain or any of the other European allies will do. Even Thatcher, the strongest European backer of Carter's tough response to the Soviet invasion of Afghanistan, does not believe she should or could force British athletes to boycott the Olympics.

Thatcher's new request will be considered by the British Olympic Committee when it meets March 4 to consider its official invitation to participate in Moscow. Committee officials have repeatedly insisted, however, that they should accept the invitation and that Thatcher should keep the government and politics out of the Olympics.

The British Amateur Athletic Board has left the decision up to individual athletes. David Shaw of the board repeated today that "if athletes themselves want to go, that's great for us and if they don't we will respect their views. Of course, there are athletes who want to go. It is their life."

Thatcher, asked in Parliament why she was "attempting to penalize" British athletes because of the Afghan crisis, replied, "These Moscow Olympics, like their predecessor in 1936 in Nazi Germany, will be used substantially for propaganda purposes. Athletes are just like any other kind of citizen. They have the same rights and responsibilities towards freedom and its maintenance."

Thatcher's announcement came as a surprise to her own Foreign Office which had not expected the British position to be made public until after a coordinated European stand on the Olympics could be negotiated at next week's meeting in Rome of the foreign ministers of the nine Common Market countries.

While the nine thus far have disagreed over what to do about the Olympics, with France, Denmark and Ireland most reluctant to call for a boycott, it was believed they might compromise on something like what Thatcher announced today.

Some sources have expressed concern, however, that by moving ahead of next week's meeting, Thatcher may again be seen by the other European governments as too far out in front of them too quickly in support of the United States. This could make next week's talks more difficult.

In Brussels last week, the Common Market foreign ministers warned the Soviet Union that it must "create conditions so that everyone can participate" in the Moscow Olympics. West German officials also said they could not see their athletes going to Moscow if the Americans stay at home.