A senior Catholic cardinal has opposed government's plans to legalise same-sex marriage and called it madness.

Writing an article for the Sunday Telegraph, Catholic cardinal Keith O'Brien, leader of the Catholic Church in Scotland, said the government's proposal to legalise same-sex marriage is an attempt to redefine marriage for the whole of society at the behest of a small minority of activists.

"Same-sex marriage would eliminate entirely in law the basic idea of a mother and a father for every child. It would create a society which deliberately chooses to deprive a child of either a mother or a father," he wrote.

Last year, Prime Minister David Cameron publicly supported legalising gay marriage at the Conservative Party conference.

"We're consulting on legalising gay marriage. To anyone who has reservations, I say: Yes, it's about equality, but it's also about something else: commitment," the Daily Mail quoted Cameron as saying at the conference.

"Conservatives believe in the ties that bind us; that society is stronger when we make vows to each other and support each other. So I don't support gay marriage despite being a Conservative. I support gay marriage because I'm a Conservative," he added.

But, cardinal Keith O'Brien said that the government does not have the moral authority to dismantle the universally understood meaning of marriage.

Meanwhile, Equalities Minister Lynne Featherstone said that the government does have the right to change marriage traditions.

"It is the government's fundamental job to reflect society and to shape the future, not stay silent where it has the power to act and change things for the better," BBC quoted her as saying.

Minister Lynne is set to launch a consultation on the plans to legalise same-sex marriage later this month.