Britain’s Labour party has dropped its opposition to an in/out referendum on EU membership, its acting leader has said.

Harriet Harman said her party would now support Prime Minister David Cameron's planned referendum bill, clearing a path for a UK-wide ballot by the end of 2017.

It marks an about turn for the party, which had rejected the idea under Ed Miliband's leadership during the general election campaign.

Writing in the Sunday Times, Ms Harman and the shadow foreign secretary Hilary Benn admitted voters wanted a say on membership, but warned against a "Brexit".

"We have now had a general election and reflected on the conversations we had on doorsteps throughout the country.

"The British people want to have a say on the UK's membership of the European Union. Labour will therefore now support the EU referendum bill when it comes before the House of Commons.

"The Labour Party doesn't want to see the UK stumble inadvertently towards EU exit. We will make the case for our continued membership.

"The notion that Britain's future and prosperity and security lies shutting itself off from this market and a world that is increasingly interdependent makes no sense.

"And in an age of powerful trade blocs, with the growing economies or Asia and Africa, we have more power by being in the EU than we could ever hope to have by acting alone.

"That is the argument we will make in this referendum, as the British people make their decision," she wrote.