One-party Jamaica?

Through 21 years of independence there have been many concerns about Jamaica's fragile democracy. Now there is new concern. This time, it centers on Prime Minister Edward Seaga's complete sweep of mid-December balloting giving his Jamaica Labour Party all 60 seats in Parliament. Although Mr. Seaga has announced measures to ensure democratic freedoms, Jamaica is clearly in for a spell of uneasy one-party rule.

Mr. Seaga campaigned and won victory in 1980 on charges that his predecessor, Michael Manley, and his People's National Party (PNP) were bent on making Jamaica a one-party state. He now faces the same charge.

Manley supporters argue that elections were not to be held until voter lists were revised next year. Seaga partisans claim the election was necessary because the PNP had attacked Mr. Seaga's personal integrity, demanding he resign from his second post as finance minister. Some of his supporters suggest the real reason the PNP opposed the election - and decided to boycott the vote - was that the party was in disarray.

If true, that helped make the election winnable. In holding the election, Mr. Seaga cashed in on the wave of popular support for Jamaica's role in the US-led invasion of Grenada. That support pushed aside growing discontent with the island's economic troubles.

This is not to suggest that three years of Seaga rule have been bad for Jamaica. US officials have been pleased to see the Manley-Cuba connection interrupted. Tourism has surged. But now, in the wake of the parliamentary vote, Mr. Seaga has more than the island's economic troubles to deal with. As Carl Stone, Jamaica's leading political commentator, says, ''Most Jamaicans don't accept this election as legitimate.'' It would be well for Mr. Seaga to speed preparation of the new voter registration lists and then to hold yet another election in which Mr. Manley and PNP could participate. That would give legitimacy to whatever government is elected.