Britain's opposition Labour Party says it won't try to block a referendum on whether Britain should remain in the 28-nation European Union.

The party's acting leader, Harriet Harman, offered support for the vote in a commentary in the Sunday Times — a U-turn on Labour's previous stance. The decision removes a potential obstacle to the referendum, which will be held by the end of 2017.

Prime Minister David Cameron of the Conservatives campaigned hard for the vote, making it a key policy during the May general election. Cameron won a majority in Parliament and Harman says it's now clear people want a chance to have their say.

However, Harman says Labour will still campaign hard to keep Britain in the EU, the world's largest trading bloc.