Singapore will decriminalise gay sex but protect the definition of marriage against legal challenge after Parliament on Tuesday approved changes to two bills.

A repeal of the colonial-era Section 377A of the Penal Code was passed with a majority of 93 to three votes in parliament, reported Channel News Asia.

A constitutional amendment to protect the definition of marriage against legal challenge was passed with a majority of 85 to two votes, according to the report.

Law and Home Affairs Minister K Shanmugam reiterated that the constitutional change would protect the heterosexual definition of marriage along with laws and policies based on that.

Social and Family Development Minister Masagos Zulkifli stressed that there were no plans to change the definition of marriage to include same-sex marriages, adding that it would be against the law for religious leaders or any licensed solemniser to solemnise a same-sex couple.

"One can still preach on the pulpit their beliefs about homosexuality or family, even if others might disagree. But no one should incite violence or hate towards others," the report quoted him as saying.

He added that religious organisations, as owners of their premises at places of worship, have the discretion to refuse same-sex solemnisations or weddings to be held on their premises.

"In exercising religious freedom, we must understand that we are also members of a plural society," the minister said.

"We must graciously accommodate those who have different values from us. Gay people are members of our society and have access to the same opportunities and social support as other Singaporeans," he added.

Turning to schools, Masagos said Singapore's education policies and curriculum remain anchored on prevailing family values and social norms, which include the family as the cornerstone of the country's social fabric, and marriage between a man and a woman.

"With the passing of two Bills ... We have created space for society to deliberate on social issues within the political process, and not through a legal route which is zero-sum in nature," the minister said.