Hardline Tory Eurosceptics determined to get Britain out of the European Union could set the party on a route to “political suicide”, the former Conservative chairman warned today.
Lord Patten, now the BBC's chairman, also urged fractious MPs to rally behind David Cameron, telling them: “Parties that don't look united don't win elections.”
He said it would be “perfectly possible” for Mr Cameron to renegotiate the terms of Britain's membership of the EU that should be acceptable to the country.
But he added: “If your response to that is that nothing would be acceptable, then I think that would be bad news for the Conservative Party.
”If nothing is acceptable, I recall Winston Churchill's very wise observation that the problem with political suicide is that you live to regret it.“
Speaking at a Westminster lunch, Lord Patten, who is also a former European Commissioner, said displays of disunity could sink the Tories' chances at the next election.
He said: ”It is very difficult to lead any party which is not united and win an election.“
Meanwhile, Labour announced it would abstain in a Commons vote next month on holding a referendum on EU membership.
A Conservative backbencher, James Wharton, has tabled a private member's bill requiring an in-out referendum to be held by the end of 2017 with Mr Cameron's support.
Labour today dismissed it as ”a Tory gimmick and a political stunt“ and said its MPs would not turn up to vote on it on July 5.
Grant Shapps, the Conservative chairman, said: ”Ed Miliband has made clear yet again he is too weak to give his MPs - let alone the public - a say.“