British Home Secretary William Whitelaw has decided not to release the ashes of Poland's wartime leader, Gen. Wladyslaw Sikorski, for return to his homeland for a state funeral that had been planned by the Poles on the anniversary of his death next week.

The decision, made after months of lobbying from both sides, will delight most of the 100,000 Polish emigres living in Britain but may infuriate authorities in Warsaw and particularly -- the Roman Catholic Church figures who had made elaborate plans for a reburial ceremony in Krakow.

The British Home Office, which has responsibilities for disinterment under an act of 19857, denied tonight that a decision had been made but insisted, as it has for several weeks, that one would be made in "the next few days." A spokesman said, however, that the government would give "full weight" to the many requests from expatriate Poles to leave the general in peace.

Although it is understood that the Polish ambassador has been orally informed of the decision, a spokesman said today that nothing could be said until written confirmation had been received.

But the "official" Polish position in recent weeks has been that Sikorski has been forgiven his well-known and virulent anticommunist stance and that the country, in the words of President Henryk Jablonski, now wished to pay tribute to his patriotism. The view in Warsaw is that the ashes of the general, who was cremated after an air crash over Gibraltar in July 1943, are "temporarily buried" in Britain.

The reaction of interested Warsaw officials last night was consternation bordering on incredulity. One said that 35 million Poles felt strongly that the general should be reburied in his homeland and would have a hard time understanding why the British, with whom Poland has a friendship treaty were acting this way.

The issue was raised by Polish Foreign Minister Joszef Czyrek when he was in London for talks last week. The British foreign secretary, Lord Carrington, is understood to have said he understood the importance of the issue.

An application for a license to exhume the ashes was filled in by Sikorski's brother-in-law, Maj. Marceli Kycia, who is now 85 and infirm but who vigorously supports the Polish government's effort to repatriate them. He told a news conference at the Polish Embassy three months ago that he was acting in accordance with the will of Sikorski's widow, who died 10 years ago.

Polish authorities have spent several months drawing up elaborate plans for the reburial ceremony. The anniversary of Sikorski's death -- July 4 -- which the Catholic authorities were so anxious to commemorate, coincided with the anniversary of the consecration of the Krakow cathedral.

Their aim was that the ashes would be buried in a sarcophagus, designed by the winner of a national competition, in the crypt of the cathedral, alongside the remains of other Polish heroes. The ashes were to have been flown from Britain to Krakow by a Polish Air Force aircraft. This would have been the first landing on British soil by an airplane from the Warsaw Pact.