A climate of militant antiradicalism - even vigilantism - is rising here in the Caribbean in the wake of the United States-Caribbean invasion of Grenada. At least two Caribbean prime ministers, Edward Seaga of Jamaica and Tom Adams of Barbados, are taking hold of this antileft feeling and turning it against their radical, left-of-center opposition.
In a move that is provoking charges of ''witch hunting'' and ''McCarthyism,'' Prime Minister Seaga recently read a list to the Jamaican Parliament of 25 citizens and permanent residents whom he called ''security risks.'' Most of the people on the list were associated with the main opposition party, the People's National Party (PNP), led by radical former Prime Minister Michael Manley.
But some people on the list had no particularly strong political connections. They included a prominent doctor whose error apparently was attending an international conference in Cuba. In what some see as a related move, the government-controlled National Bauxite Institute dismissed Joseph Manley, son of Michael Manley.
Some observers fear these moves may be an opening round of a campaign of intimidation against the Jamaican PNP - one intended to undermine that party before the elections that are to be held in two years.
In Barbados, Prime Minister Adams has revoked the work permit of Guyanese journalist Ricky Singh, editor of the Caribbean Contact, a monthly paper put out by the Caribbean Council of Churches and widely read by area intellectuals. Singh and his paper were the only major news media voice to come out against the intervention in Grenada, in which Barbados played a major role.
Singh has been given until Dec. 2 to leave the country. The journalist said that in an interview he had with Adams on Nov. 9, the prime minister accused him of having links to the DGI, the Cuban security agency. Singh denies the accusation.
There have been reports that police searched the homes of at least three leaders of a left-wing, largely student group called Monali. These people reportedly were interrogated for several hours. They are Francis Bell, a student; Ricky Parris, a leader of the Barbados Workers' Union; and Norman Farrier, a free-lance journalist who edits Monali's newspaper.
Intense debates have been going on in the Barbadian parliament. Progovernment deputies spoke of radical ''foreigners'' (Guyanese, Jamaicans, Trinidadians, and others) who should leave the island. And a progovernment deputy accused a member of parliament of being a ''communist'' because he had a son named Fidel. In response, an opposition deputy warned ''not to fall into the trap of thinking that people are unpatriotic because they do not agree with the prime minister.''
In a more personal incident, this reporter was mistaken for a Cuban when arriving at a restaurant in St. Lucia for a lunch date with an area politician. Several diners moved to phone the police when they saw me.
An American observer says the roots of antileftism and vigilantism predate the Grenada invasion. He thinks they are grounded in an attitude in much of the English-speaking Caribbean that ''turns each prime minister into a little king, thus turning dissent into lese majesty.''