British lawmakers vote for the first time Tuesday on legislation underpinning a referendum on whether the country should leave the European Union, due by the end of 2017.
Foreign Secretary Philip Hammond will give a speech to open the debate on the EU Referendum Bill at 12:30 pm (1130 GMT) before the House of Commons spends the day debating and voting on it.
Prime Minister David Cameron's government is expected to win the vote easily but the bill must pass through several other stages in parliament before becoming law.
The referendum, which could be held as early as next year, was triggered when Cameron's centre-right Conservatives won a majority in last month's general election and is now one of the top items on his legislative agenda.
The prime minister is holding a wave of talks with other European leaders in a bid to secure reforms to the EU which he says are necessary ahead of the referendum.
Cameron says he will vote in favour of remaining in the EU if he can secure these changes, which include making it harder for EU migrants to claim state benefits in Britain.
Opinion polling currently suggests that voters in Britain would back staying in Europe.
The Commons vote comes after comments by Cameron triggered a row over whether ministers in his government would have to resign if they did not campaign for Britain to stay in the bloc.
He said on Sunday: "If you want to be part of the government you have to take the view that we are engaged in an exercise of renegotiation to have a referendum and that will lead to a successful outcome."
That was interpreted by media and some eurosceptic MPs from Cameron's party as meaning that those who wanted to vote against EU membership would have to quit the government.
But Cameron's spokeswoman played down the row by insisting he had not yet decided whether ministers would be allowed to campaign on different sides in the referendum.
She said he had been referring to the need for collective responsibility during the renegotiation process, not during the referendum campaign.