Mayor of London Boris Johnson has launched another robust defence of the government’s policy on equal marriage.

Earlier this summer, Mr Johnson released an Out4Marriage video, saying that he saw “no reason” why the “happy state” of marriage should be denied to “anybody”.

Writing in the Independent, Mr Johnson expanded on some of the themes raised in his video and said:

“I have been asked to say something more in favour of gay marriage — and I do so gladly, because frankly I can’t see what the fuss is about.

“A couple of years ago someone asked whether I supported the idea and I was a bit flummoxed, because I thought it was already legal”.

In a week where the religious opponents of equal marriage have dominated the headlines following the highly out spoken remarks of Lord Carey, Mr Johnson said:

“Marriage is an ancient human institution that is far older than any of the religions that are practised today.

“It may well be beloved by God, but no religion has ever had a monopoly on marriage”.

On Monday, the former Archbishop of Canterbury Lord Carey, accused politicians of plundering the “sacred institution” during a fringe event at the Conservative Party Conference in Birmingham.

In his article, Mr Johnson stressed how the government was maintaining religious freedom under the plans, saying: “There is no call for gay marriage to be politically imposed on churches or mosques or any other religious institutions — or, if there is such a call, it is emphatically not one I would support”.

Mr Johnson’s intervention comes after Downing Street gave a strong indication that Prime Minister David Cameron was keen to press ahead with legislation – despite last weekend’s poll showing that a significant number of grass roots party chairmen were unhappy with the plans.

In 2010, Mr Johnson became one of the first senior Conservatives to back same-sex marriage, telling PinkNews.co.uk: “If the Conservatives and Liberals [Liberal Democrats] can get together in a national coalition and settle their differences, I don’t see why you can’t have gay marriage.”

Labour leader Ed Miliband followed in the footsteps of Mr Johnson and Lib Dem leader Nick Clegg in releasing an Out4Marriage video last month.