MPs have approved legislation for same-sex marriage in England and Wales, despite the opposition of dozens of Conservative MPs.
The Commons voted in favour of the The Marriage (Same Sex Couples) Bill, by 400 to 175, a majority of 225, at the end of a full day's debate on the bill on Tuesday.
Prime Minister David Cameron described the move as "an important step forward" that strengthens society. But about 140 of his Conservative MPs are thought to have voted against the plans.
Former children's minister and Conservative MP Tim Loughton told the BBC that he believed "140 or so" of his party colleagues had voted against the plans, along with "a small rump of Labour MPs" and "four Lib Dem MPs".
"Apparently there are 132 Conservative MPs who voted in favour, so I think what we're going to see is that more Conservative MPs voted against this legislation than for it."
Deputy Prime Minister and Lib Dem leader Nick Clegg said: "I genuinely believe that we will look back on today as a landmark for equality in Britain. Tonight's vote shows Parliament is very strongly in favour of equal marriage.
"The Liberal Democrats have long fought for equal marriage. It is party policy and I am proud that the Liberal Democrats are part of the coalition government that are making it happen."
Opposition leader Ed Miliband said: "This is a proud day and an important step forward in the fight for equality in Britain.
"The overwhelming majority of Labour MPs supported this change to make sure marriage reflects the value we place on long-term, loving relationships whoever you love."
MPs were given a free vote on the bill, meaning they were not ordered to vote for or against by party whips. Their decision to back the bill at second reading signifies that they approve of it in principle. The legislation will now receive more detailed parliamentary scrutiny.