Malta's democracy is cast in doubt

Can the island of Malta still be accurately described as a democracy? Or is it a rigidly controlled state in which political opposition is no longer accepted?

These questions have become a focus of international attention since Malta's Prime Minister Dominic Mintoff, leader of the Labor Party, banned contacts between foreign embassies and members of the opposition Nationalist Party.

The prime minister imposed the ban in January after expressing irritation that foreign diplomats were in touch with the Nationalists under their leader, Edward Fenech Adami.

The ban has drawn attention to the fact that since the 1981 general elections , the Nationalist Party has failed to take its seats in the Maltese Parliament. When the elections were held, the Nationalists gained 51 percent of the vote, but won only 31 seats out of a total 65. They protested that Mr. Mintoff had rigged constituency boundaries in the Labor Party's favor, enabling him to keep the Nationalist Party from power.

At first the Nationalists boycotted parliamentary sessions and demanded fresh elections under new rules. Mintoff refused and last April declared all Nationalist-held parliamentary seats vacant.

But Mintoff did not stop there. He has also refused to give the Nationalists access to Maltese radio and TV stations. When Mr. Fenech Adami made arrangements to broadcast from a TV station in nearby Sicily, Mintoff countered by pushing through a ''foreign interference act'' banning broadcasts by Maltese citizens from outside the island.

The embargo on contacts between foreign diplomats and the Nationalist Party is seen as a further attempt to make political opposition impossible.

The United States ambassador to Malta, James Rentschler, has refused to accept the validity of the ban, arguing that it violates the Vienna Convention on Diplomatic Relations, which grants civil and criminal immunity to foreign diplomats. Even the government of Libya, with which Mintoff has attempted to maintain good relations, joined in the protest.

Foreign diplomats in the capital city of Valletta argue that the ban isolates them from over half of Malta's population of 320,000 people. Some have canceled their National Day celebrations, claiming that Mintoff's refusal to allow Nationalist Party supporters to attend would make nonsense of such events.

Observers in Valletta say Mintoff is under heavy pressure from senior Labor Party figures to make life as difficult as possible for Fenech Adami and his followers. They apparently fear that if the Nationalists are allowed to organize they will gain political support.

Foreign diplomats are said to be maintaining discreet contacts with Mintoff's political opponents despite the ban. Diplomats report fear among the Nationalists that the prime minister is devising still more ways of preventing the opposition from operating effectively.

Mintoff, a fiery orator and skilled negotiator, was voted into office in 1971 and soon began attacking opposition newspapers. He was also accused of manipulating law courts on the island.

Malta's strategic situation between Sicily and Libya has aroused Soviet interest. In 1979 Mintoff evicted the last British troops from Malta. Soon afterward Mintoff decided to allow Soviet commercial ships to stock large quantities of oil in what used to be NATO storage tanks near Valletta.

Malta is a tourist center for Europeans seeking winter sunshine, but more and more Mintoff has had to rely on grants from foreign governments to maintain the economy.