Tommy Koh, ambassador-at-large in the Singapore foreign ministry, made the comments on Facebook in response to a post about Thursday's historic ruling, which followed a decades-long campaign against the law in the South Asian nation.

"I would encourage our gay community to bring a class action to challenge the constitutionality of Section 377A," Koh said, referring to the law which criminalises sex between men.

Responding to a comment that previous petitions to strike down the law were unsuccessful, Singapore's former US ambassador and envoy to the United Nations said: "Try again."

While Singapore boasts a modern and vibrant culture, attitudes towards homosexuality remain conservative. Sex between men remains technically illegal under a law dating back to British colonial rule, although the statute is rarely enforced.

Despite the challenges, support for gay rights has been growing in recent years in the city-state of 5.6 million. Huge crowds attended the 10th anniversary of Singapore's annual Pink Dot gay rights rally in July.

Pink Dot, Singapore's leading gay rights group, said the Indian ruling showed attitudes towards homosexuals were "positively changing in Asia" and called on parliament to decriminalise gay sex.

In 2014, Singapore's highest court dismissed a constitutional challenge to the law and said it was up to parliament to repeal it.

Singapore Law and Home Affairs Minister K. Shanmugam said the government was caught in between a majority of Singaporeans opposing the repeal of the law and a "growing minority" who want it abolished.

"Really I think society has to decide which direction it wants to go," he added. "The laws will have to keep pace with the changes in society."