Mr Goh said the tightly controlled city-state should ease into greater political freedoms and giving freedom too fast had caused problems when the Soviet Union first opened up.

"I know some people want even greater freedom," Mr Goh said during a National Day rally speech.

"But where politics is concerned, I prefer to ease up slowly rather than open up with a big bang. When Gorbachev opened up the Soviet Union with his glasnost, the Soviet Union collapsed with a big bang."

Mr Goh said Singapore should "pump the air into the political balloon slowly".

He said he didn't want to be known as "Goh Ba Chev," after Mikhail Gorbachev, who introduced democratic reforms in the communist state.

Singapore has been widely criticised for its strict social and political controls.

But the country's leaders – often held up as being among the world's most efficient and least corrupt – say their policies have helped make Singapore one of Asia's most stable and prosperous countries.

Mr Goh said Singapore's Speaker's Corner – opened last September in a public park – and several political discussion groups provided outlets for different views in the city-state.

However he said an outspoken civil rights group, the Think Centre, was one-sided and would not be ignored.

"If the government thinks something they said will hurt Singapore, it has to rebut them, if necessary, forcefully.

"But this should not be seen as the government smothering free expression. The government will not regard you as an opponent unless you choose to be one."

A single political movement, the People's Action Party, has ruled Singapore since independence in 1965.

Mr Goh delivered the annual speech at a university instead of the usual indoor theatre because the musical Miss Saigon was playing there.

The government even allows foam parties, he said. Scantily-clad Singaporeans and foreigners dance in a giant bubble bath on the beach during occasional foam parties on Singapore's Sentosa island.

"I thought foam parties were for children, but I saw pictures of adults enjoying themselves too," he said.

"That is all right, so long as the merrymakers prance around with the lights and their clothes on."

AP