British officials said today they have received no formal request from the Reagan administration to impose economic sanctions against Libya, and repeated the government's belief that such measures are ineffective and often counterproductive.

"We are not very confident sanctions would have much effect" on Libyan leader Muammar Qaddafi, "or on anybody else," said an official involved in this country's antiterrorism strategy. "They are a very blunt instrument."

Other Europeans, also commenting before President Reagan's speech, matched British restraint.

In Paris, West German Foreign Minister Hans-Dietrich Genscher noted the "very cautious" attitude of his government toward economic sanctions.

At a joint press conference with Genscher, French Foreign Minister Roland Dumas said the French government was awaiting details of Reagan's proposals tonight, adding that "France would hope that the rules of international law would be applied" if convincing evidence were found that a country had aided or participated in a terrorist attack.

In Vienna, where a terrorist attack at the airport Dec. 27 killed three persons, Foreign Minister Leopold Gratz told reporters that Austria would consider joining sanctions against any nation shown to have backed the assault. "There may be other reactions" besides sanctions, he added.

[In Ottawa, Canadian government officials said Canada would not join the United States in imposing economic curbs because of the limited impact of such a move, Reuter reported.]

In a session with American journalists yesterday, Antony Acland, ambassador-designate to Washington, said that Britain "already has certain restraints on what we sell to Libya. We show our disapproval of the Libyan regime."

"Sanctions don't work," Acland said. "They didn't work in Zimbabwe," under the white Rhodesian regime, "they don't work in South Africa, and we don't think they would be very effective in the case of Libya."

Prime Minister Margaret Thatcher has come under criticism within the Commonwealth, where her government was the only one of 49 nations during the Commonwealth conference last fall to oppose sanctions against South Africa.

Amplifying Thatcher's overall stand rejecting economic sanctions as a diplomatic weapon, the antiterrorism official said today that Britain has "a difference in view" with the Reagan administration.

"Unless everybody participates," he said, "you can end up shooting yourself in the foot."

At the same time, he said, economic sanctions "only work if the goods can be easily traced." In the case of Libya's oil exports, he said, "they are on the high seas, and oil can change hands 100 times" before reaching its destination.

While the subject "has certainly been discussed" in Washington, he said, the administration had not formally requested British participation in any sanctions against Libya.

This official, and Acland, pointed out that Britain took measures limiting its ties with Libya in the spring of 1984, when shooting from within the Libyan Embassy here into a London square left a policewoman dead.

In addition to breaking diplomatic relations, leaving its affairs in the hands of an interest section inside the Italian Embassy in Tripoli, Britain ended all new defense sales to Qaddafi and said that it would review all existing contracts.

At that time, Foreign Secretary Geoffrey Howe described the severence of relations as "the ultimate sanction," and noted that "the United States Embassy in Tripoli was burnt down in December 1979, yet it was not until 1981 that diplomatic relations were suspended. Even then, they were not broken."

Although in his 1984 statement Howe said that there were 10,000 Britons living in Libya, officials said today that that figure has decreased to 5,000. Trade figures for the first 10 months of 1985 included slightly less than $300 million worth of British exports to Libya. During the same period, British imports from Libya totaled about $370 million.