The Soviet Union today blamed Britain for the Falkland Islands crisis and called "inadmissible" any British military effort to recover the disputed territory from Argentina.

A commentary in the Communist Party newspaper Pravda accused the government of Prime Minister Margaret Thatcher of pursuing the "gunboat diplomacy" of Britain's colonial past and pointedly recalled "the ignominious failure" of another British Conservative government when it attempted to recover the Suez Canal in 1956.

After more than a week of studious neutrality, the commentary today came close to endorsing Argentina's claim on the islands. However, Pravda insisted that the issue must be resolved by negotiations.

The government-controlled media here has been focusing on British military preparations caused by the Argentine takeover of the islands while avoiding any criticism of the Argentine action.

Since then-president Jimmy Carter imposed a partial embargo on U.S. grain exports to Moscow following the Soviet invasion of Afghanistan in December 1979, the Soviets have vastly expanded their trade relations with Argentina. Figures for the first nine months of last year show Soviet purchases in Argentina near $3 billion. The two countries have concluded various agreements on Soviet purchases of Argentine grain, meat and wool. Argentina has been negotiating to buy enriched uranium from Moscow for an experimental reactor near Buenos Aires.

Pravda today charged that the Thatcher government has deliberately embarked on the course of military action because of domestic economic difficulties.

"An excessive escalation of the present crisis by London reveals the desire to cover up the failures of the conservative government in domestic policies.

"But surely this is not a reason for unleashing a war . . . ," the commentary said.

Other Soviet commentaries supported Argentina's claim to sovereignty over the islands, saying that Britain may be trying to hang on to the remnants of its empire because of supposed oil and gas deposits around the Falkland Islands.