Update: British lawmakers voted overwhelming in favor of a gay marriage bill on Tuesday. In an initial vote, Members of Parliament backed it in a 400 to 175 vote.

Earlier...

UK lawmakers will vote Tuesday on a gay marriage bill which has been backed by Prime Minister David Cameron, but has caused division in his Conservative Party.

Members of Parliament (MPs) are currently debating the bill in the Commons, and the vote is expected at 2 PM EST.

BBC News explains:

The Marriage (Same Sex Couples) Bill would enable same-sex couples to get married in both civil and religious ceremonies, where a religious institution had formally consented, in England and Wales.

It would also allow couples who had previously entered into civil partnerships to convert their relationship into a marriage.

"The depth of feeling, love and commitment is no different between same-sex couples than opposite-sex couples," the Associated Press reports Culture Secretary Maria Miller as saying. "This bill enables society to recognize that commitment in the same way, too, through marriage."

Ed Miliband, the leader of the opposition Labour Party, said Monday, “I’ll be voting for equal marriage for a very simple reason: I don’t think that the person you love should determine the rights you have."

George Osborne, William Hague and Theresa May, the most senior members of the Cabinet, wrote a letter to the Telegraph urging support for the gay marriage bill, writing, in part:

Attitudes towards gay people have changed. A substantial majority of the public now favour allowing same-sex couples to marry, and support has increased rapidly. This is the right thing to do at the right time.

The AP and CNN report that the bill is likely to pass today with support from Labour and the Liberal Democrats.

The Guardian's Andrew Sparrow is live blogging the debate here.