LONDON (Reuters) - Prime Minister David Cameron is "losing control of his party", Conservative Party grandee Geoffrey Howe said on Sunday, as a row raged over whether a close aide to Cameron had labelled grassroots activists "mad, swivel-eyed loons".
The furore threatens to further alienate Cameron and his inner circle from the core of his party, with whom ties are already almost at breaking point.
Differences with the grassroots over Britain's membership of the European Union and Cameron's support for legalising same-sex marriage have raised questions over his leadership and could hurt the party's chances in the next election, due in 2015.
"Sadly, by making it clear in January that he opposes the current terms of UK membership of the EU, the prime minister has opened a Pandora's box politically and seems to be losing control of his party in the process," Howe wrote in an article for the Observer newspaper.
Howe was former prime minister Margaret Thatcher's longest-serving cabinet minister, but fell out with her over relations with Europe and is best remembered for a scathing resignation speech that helped topple her as leader in 1990.
Cameron's Conservatives have been rattled by the surging popularity of the UK Independence Party (UKIP), whose main aims are to pull Britain out of the EU and curb immigration.
Its rise has fuelled a heated national debate over whether Britain derives sufficient benefits from EU membership to outweigh the financial cost and the ceding of some important powers to Brussels, like the ability to limit immigrants from the other 26 countries in the union.
An opinion poll by pollster ComRes for the Sunday Mirror and Independent on Sunday newspapers put support for UKIP at 19 percent, which ComRes said was the highest level the party had achieved in any survey yet.
The opposition Labour party led with 35 percent, while the Conservatives were on 29 percent and their Liberal Democrat coalition partners on 8.
"The ratchet-effect of Euroscepticism has now gone so far that the Conservative leadership is in effect running scared of its own backbenchers, let alone UKIP," Howe said, referring to the hundreds of rank-and-file Conservative members of parliament who occupy the rows of seats behind Cameron and his ministers.
In January, Cameron promised that if the Conservatives won the 2015 election they would call a national referendum in 2017 on whether Britain should stay in or leave the EU. But that did not go far enough for many Conservatives, who last week forced him to back a new bill that would enshrine it in law.
The Conservatives' restive right wing also last week voted to criticise the government's legislative agenda for not including such a bill in the first place, an unusual move in British politics that embarrassed Cameron.
Compounding Cameron's problems are media reports that an un-named close aide, at a private dinner last week, described the Conservative grassroots as "swivel-eyed loons".
Cameron's office says the comment did not come from them, and insist the prime minister is still in charge of his party.
The row comes at an especially bad time for Cameron, whose flagship bill to legalise same-sex marriage will be debated in parliament this week. Conservative activists wrote to Cameron on Sunday warning that the move would boost UKIP's membership.
"The prime minister seems to have gathered around himself a metropolitan elite who seem to inhabit a different planet to most of us ... Droves of previously loyal Conservative Party members are leaving," Bob Woollard, chairman of the Conservative Grassroots umbrella group, told the BBC.
Cameron says he would like to do more to satisfy the Conservative core, but is held back by being in coalition with the left-leaning Lib Dems.
Ties between the two parties have frequently come under strain since they teamed up in 2010, but they have pledged to stay together to help revive Britain's weak economy.
However, in an article published on Sunday, Cameron hinted that he could end the partnership before the 2015 election.
"Can we improve the state of the country? Can we fulfil our manifesto? The best way to do that is to continue with the coalition, but if that wasn't the case then we'd have to face the new circumstances in whatever way we should," he told Britain's Total Politics magazine.
(Editing by Mark Trevelyan)