The United Nations has decided to stand by its appointment of a Soviet U.N. official to the sensitive post of personnel director for U.N. headquarters here following a U.N. investigation into allegations that he is a Soviet intelligence agent.

Swiss authorities, however, announced yesterday that they are still conducting their own investigation of alleged KGB agent Geli Dneprovski to determine whether to issue him an entry visa for Switzerland. A spokesman for the federal Department of Justice and Police said that the Swiss government would make its decision within the next two weeks.

Despite protests from the United States and Britain, the United Nations has decided to push ahead with the appointment on the ground that the U.N. investigation of the official produced no evidence that he is in Soviet intelligence. According to diplomatic sources, American and British officials have told the United Nations they are satisfied that Dneprovski is a KGB agent, confirming allegations that first appeared in the Western press after the defection to London of Vladimir Rezoun, who was an intelligence agent at the Soviet mission in Geneva.

According to diplomatic sources, the Americans and British also argued that the post should not be held by a national of either superpower. The office, which has traditionally been filled by a representative a Third World nation, provides access to confidential files and plays an influential role in deciding appointments throughout the U.N. system.

The United Nations has been under Soviet pressure to maintain the appointment, according to diplomatic sources here. The international body also appears to be talking the line, according to these sources, that it will not cave in to a press campaign on spy allegations at variance with the organization's own investigation.

Officially, the large U.N. office here is making no comment on the case. "I have nothing to do with this," Luigi Cottafavi, the director general of the Geneva office, adding that the matter is the responsibility of the New York headquarters.

Whether or not Dneprovski takes his post depends now on the Swiss government's decision on his visa. Yesterday's announcement from Bern came less than two weeks after the Swiss, in an unusual move, asked the International Labor Organization to oust a Soviet official, Gregori Miagkov, who has also been alleged in press reports to be a KGB agent. In demanding that Miagkov leave Switzerland, the Swiss government invoked the national security clause of a 1946 agreement with the International Labor Organization, which has its headquarters here.

"The kickout [of Miagkov] suggests they are in a tough mood," observed a Western diplomat.

Since the defection to London of the Geneva based Soviet agent Rezoun a little over two months ago, a spate of Western reports has named alleged KGB agents in Geneva's internation organizations, which are a fertile hunting ground for recruiting agents for Third World countries. American, British and Swiss authorities, however, will not publicly confirm who is making the allegations and the picture is complicated further since a high-ranking Soviet U.N. official, Araki Schevchenko, defected in New York in April.

Meanwhile, two Soviet officials, Miagkov and Vladimir Bourkeev, have left the ILO in recent weeks amid reports that they were involved inthe KGB. Another alleged Soviet spy still occupies his office as director of conference and general services, but there are rumors here that other Soviets will soon be leaving for Moscow to avoid embarrassment.