Relations between major West European nations and Moscow have plunged to a new low with a series of expulsions of Soviet diplomats accused of spying. In the most dramatic case, France kicked out 45 Soviet diplomats and two journalists on Tuesday. Five days earlier, Britain expelled the second secretary and deputy air attache at the Soviet Embassy in London, as well as the correspondent of the Soviet magazine New Times.
That same day, the Spanish government asked a Soviet diplomat to leave the country on charges of ''engaging in activities incompatible with his status'' - diplomatic language for espionage. And the Italians continue to press doggedly ahead with their investigation of the alleged ''Bulgarian connection,'' possibly linking the 1981 shooting of Pope John Paul II to the Kremlin.
The new wave of expulsions shows that governments in Paris, London, and Madrid are determined to crack down on Soviet officials who use their diplomatic status as a cover for spying. Unconfirmed reports said that action by the British and French governments followed information from recent Soviet defectors , possibly including fugitive members of the KGB, the state security police.
The expulsions come at a particularly sensitive time in East-West relations in Europe. The lack of progress in United States-Soviet Union missile talks in Geneva has dashed hopes that Soviet leader Yuri Andropov would bring new flexibility to his country's negotiating position. The prospect of an impasse in Geneva, followed by installation of US Pershing II and cruise missiles in West Europe, has given fresh impetus to the ''peace movement,'' which staged big demonstrations through much of West Europe over Easter.
But, far from being overawed by the unyielding Soviet position, West European governments as a whole have decided that if Moscow is going to play it tough, so will they.
France has been particularly strong in insisting on a need to build up allied nuclear forces to match those of the Soviet Union. This might appear paradoxical since France does not belong to NATO's integrated military structure and the government in Paris includes two Communists.
But ever since he took office in May 1981, French President Francois Mitterrand has pursued an unyielding line toward the Kremlin. The Socialist leader has proved President Reagan's stoutest supporter on the Continent for the past two years in this respect - a dramatic change from the time when his conservative predecessors tried to act as inter-mediaries between Moscow and the West.
The hostility that the Kremlin now shows toward France does not worry Mr. Mitterrand too much. His foreign minister, Claude Cheysson, paid a visit to the Soviet Union in February, at which time he had a frosty meeting with Mr. Andropov. France still insists that relations between Paris and Moscow cannot become normal until Soviet troops leave Afghanistan and Moscow-backed military rule ends in Poland. After the expulsions Tuesday, the previous chill in relations is bound to turn into a deep freeze.
The French Interior Ministry, which handled the matter, accused the Soviet diplomats of widespread scientific, technical, and technological espionage, particularly in the military field. Its net took in the head of the Paris bureau of the Soviet news agency, Tass, and his assistant as well as the diplomats, headed by the embassy's first secretary, Nikolai Chetverikov.
Mr. Chetverikov said that he first learned of the impending expulsion from a morning newspaper. Official confirmation of the decision was delivered to the embassy in mid-morning. In the early afternoon, the diplomats were driven to Charles de Gaulle Airport in two minibuses, which took them right up to a waiting Soviet airliner. A statement from the embassy described the French decision as ''totally unfounded and arbitrary.'' Mr. Chetverikov insisted that it was ''a political decision.''
The Interior Ministry refused to elaborate on its brief statement announcing the expulsions. It is known, however, that French counterintelligence agents have been keeping a particularly close watch on Soviet diplomats in recent months. They scored a success at the end of March with the arrest of a Frenchman said to have been passing industrial secrets from state-owned firms to members of the Soviet Embassy.
French newspapers also speculated that the expulsions might be connected with the murder of a counterespionage agent, Lt. Col. Bernard Nut, in mid-February. Mystery has shrouded the case ever since Nut's body was found near the Mediterranean city of Nice on Feb. 15.
French intelligence sources say Colonel Nut was on a mission when he died. His particular sphere of activity was Italy. French newspapers have speculated that he was involved in investigating the ''Bulgarian connection'' that the Italians say was behind the assassination attempt on the Pope in 1981, at the instigation of the KGB. Nut was shot just after a Soviet airline official was arrested for spying in Rome. The press here suggest the murder might have been carried out by a double agent in retaliation for Nut's activities in Italy.
The scope of the French expulsions makes it clear that the Mitterrand administration was determined to go beyond picking up Soviet officials one by one on the basis of individual cases. The President and his tough-minded interior and decentralization minister, Gaston Defferre, were determined to take a step that would convince Moscow that France means business.
In this case, the business concerned was espionage. But the French action, together with the recent expulsions in Spain and Britain, also form part of a steady toughening of West Europe's attitude toward the Soviet Union as Afghanistan remains occupied, Poland is run by its generals, and the Soviet attitude on missile reductions appears as unbending as ever.