Image caption John Major said it was in Britain's interest to remain with the EU

Sir John Major has endorsed David Cameron's EU referendum plan - but admitted it is a "gamble" for the country and the Conservatives.

Mr Cameron has pledged to hold an in/out referendum on Europe if he wins the next general election.

The former prime minister said the move could "heal sores" and have a "cleansing effect" on politics.

Labour said his comments confirm Mr Cameron's EU policy is designed to manage a "divided Conservative Party".

The prime minister wants to renegotiate the terms of Britain's relationship with Europe before putting it to a public vote by 2017 at the latest.

Sir John said it was right to let the electorate decide whether to approve a renegotiated settlement or "pull us out altogether".

Lessons from the past

"At present, we are drifting towards and possibly through the European exit. We need a renegotiation and a referendum endorsement of it. If this is denied, the clamour for it will only grow.

"But it is a gamble for the country and for the Conservative Party. The relationship with Europe has poisoned British politics for too long, distracted Parliament from other issues, and come close to destroying the Conservative Party. It is time to resolve the matter," he said.

The Parliamentary [Conservative] Party includes irreconcilables who are prepared to bring down any government or any prime minister in support of their opposition to the EU Sir John Major, Former Conservative PM

The former PM said he took the view that it was in Britain's national interest to stay in the EU - and he believed the "vast majority" of voters could be persuaded to support continued membership.

Sir John - whose own time as Tory leader was wracked by backbench rebellions over Europe - warned the PM to beware of MPs "with Conservative heads and Ukip hearts", who will settle for nothing less than EU withdrawal.

"I learned 20 years ago that the parliamentary party includes irreconcilables who are prepared to bring down any government or any prime minister in support of their opposition to the EU."

He suggested appointing a "lead negotiator" in Cabinet to represent the PM across EU capitals in negotiations.

But he cautioned the party against giving advice to Mr Cameron in public because it will look like he is "acting under political duress".

"I know that because I have been there: advice, yes that is a proper role for parliamentarians but the truly well-meaning will give him advice in private."

Responding to the speech, shadow foreign secretary Douglas Alexander said: "John Major has acknowledged today that David Cameron's gamble on Europe is much more about managing a divided Conservative Party than what's best for Britain."

Mr Cameron's approach "risks creating instability and undermining future investment", he added.