However, a large Tory vote against gay marriage will not help the party appeal to centre ground voters. Mr Osborne warned last week that ditching the policy would be toxic electorally.
He said that polls indicate a "clear majority" in favour of the change, particularly among the young and women.
In an analysis of Barack Obama's victory in last week's US presidential election, Mr Osborne said that Mitt Romney's prospects were undermined by the sense that the Republicans were out of step with modern America on social issues such as abortion and gay marriage.
"It is worth reflecting that in Britain, as in America, a clear majority of the public support gay marriage, and an even bigger majority of women support it. That majority support is just as high in the North as it is the South, and it is equally high among all socio-economic groups," he wrote in The Times.
"Successful political parties reflect the modern societies they aspire to lead. As Margaret Thatcher said in the first sentence of her introduction to the 1979 Conservative election manifesto: 'The heart of politics is not political theory, it is people and how they want to live their lives'."
-AAP
