Singapore’s new law gives ministers in the tightly-regulated city powers to order internet platforms to put warnings next to posts they deem false. (AFP)

Singapore has defended a controversial new law against misinformation that it has wielded against Facebook, after an opposition party launched a withering attack on the legislation.

The law gives ministers in the tightly-regulated city powers to order internet platforms to put warnings next to posts they deem false, but activists fear it could be used to stifle dissent.

Authorities used the measure twice last month, ordering Facebook to put a correction by a post for the first time, and telling an opposition party member to correct a message.

The opposition Progress Singapore Party (PSP), which will contest elections expected within months, said the law fell short of the values of transparency, independence and accountability.

It empowers ministers “to declare a piece of news to be falsehood without requiring any justification, criteria or standards,” said the party, in a statement on their website alongside a picture of people with their mouths taped shut.

The PSP is among a host of small opposition parties but they are not seen as a threat to the People’s Action Party, which has ruled Singapore for decades.

But in a joint statement late Wednesday, the communications ministry and law ministry insisted the legislation, which came into force last month, would not curb free speech.

“Requiring a factual statement to be posted in order to correct a false statement does not curtail anyone’s free speech,” they said.

Google also cited the new regulation, which prohibits adverts seeking to influence public opinion, when it announced a ban on political ads in Singapore this month, according to another opposition group, the Singapore Democratic Party.

The party said the move would affect its ability to reach out to voters in a country where the mainstream media usually backs the government.

Singapore’s government, which regularly faces criticism for curbing civil liberties, insists the legislation is necessary to stop the spread of damaging falsehoods online.