Even as MPs agreed to hold a Commons vote on a referendum, government sources made clear that the Tories would be whipped to vote against a poll.

Mr Cameron’s decision to impose a three-line whip has angered many MPs, since the vote was called under rules the Coalition promised would give backbenchers more freedom.

The back-bench business committee yesterday voted to hold a debate on the issue on Oct 27 after more than 100,000 people signed a petition demanding a choice.

The Prime Minister, who has expressed his desire to take back some powers from Brussels, is publicly opposed to a referendum and will order his MPs to vote against it.