By Peter Griffiths
LONDON (Reuters) - Prime Minister David Cameron has ditched EU policing rules and allowed a close ally to float the idea of Britain quitting the bloc altogether, taking on Brussels in a gamble that has proved the undoing of predecessors.
The salvoes against Europe could prove popular with voters but dangerous for Cameron - exposing discord both within his historically fractious Conservative Party and between it and its junior coalition partners, the pro-Europe Liberal Democrats.
The moves have been greeted enthusiastically by the powerful right-wing press, while a senior Lib-Dem accused the Conservatives, also known as Tories, of "petulant posturing".
The island nation of Britain has been cool towards the EU for generations, staying out of both the euro common currency and the Schengen borderless zone.
But fights over Europe have also been politically lethal to a succession of Conservative leaders, ever since the party took Britain into Europe in 1973.
It is not the first time Cameron has crossed swords with Brussels - last year he vetoed an EU austerity treaty that would have applied only to countries using the euro; they were forced to adopt the treaty without Britain.
But more often than not he has sought to avoid clashes over Europe, aware of the damage the issue has wrought on the careers of other Conservative leaders, including his heroine Margaret Thatcher, brought down by party colleagues in 1990.
He has said he wants to renegotiate Britain's relationship with Europe, but does not want to abandon its biggest trading partner at a time of recession and painful public spending cuts.
However, the Conservatives are trailing ahead of an election due in 2015, and need to rally their activists and win voters from the small but growing anti-EU UK Independence Party. Letting anti-Europe politicians speak out from within the government could help that goal.
The euro zone debt crisis has emboldened the Conservatives' anti-European wing, which is agitating for Britain to use the crisis in Brussels to win back a range of powers or even leave the 27-nation union altogether.
The government set out plans on Monday to ditch 130 EU measures on law and policing, using "opt-out" powers negotiated by the previous administration.
The policing measures include European Arrest Warrant system, which helps European countries transfer suspects across borders by making extradition largely automatic. The Lib Dems support the arrangement and say it helps fight crime.
Liberal Democrat Matthew Oakeshott, a member of the House of Lords, Britain's upper house, accused the Conservatives of "petulant posturing" over Europe and said it was "red meat to the rabid anti-Europeans on the Tory right".
One of Cameron's closest allies, Education Secretary Michael Gove, was quoted in the right-wing Mail on Sunday as telling "friends" it was time for Britain to take a tougher line with Brussels and threaten to quit the EU if it does not get its way.
"We have to tell them if they don't return some of the important powers they have snaffled from us, we will leave," the Mail quoted a source as saying of Gove's views, typical British newspaper code for an authorized off-the-record briefing.
Gove's spokesman declined to comment, but other Conservatives defended the remarks attributed to him.
"The point that Michael is reflecting and many of us feel is that we are not satisfied with the current relationship between the EU and the United Kingdom," Defense Secretary Philip Hammond told the BBC on Sunday. "The balance of competencies is not right and the mood has changed."
A YouGov poll in the Sunday Times newspaper put support for the Conservatives at 33 percent, ten points behind the opposition Labour Party.
Asked how they would vote in a hypothetical referendum on Britain's EU membership, 48 percent said they would choose to leave, 31 percent would stay and 21 percent were unsure or would not vote.
Cameron has opposed an "in/out" referendum, preferring to talk about a vote on a renegotiated role for Britain in Europe.
The prime minister said last week it was time to review the balance of powers, but it would be wrong to leave the EU when the UK economy is still mired in a recession.
(Editing by Peter Graff)