100,000 sign petition calling for EU referendum
Tory and Labour MPs are among 100,000 signatories of a new petition calling for a referendum on EU membership.
It comes as about 80 Tory MPs prepare to discuss ways of pressing for a renegotiation of the UK's position.
Conservative grandee Lord Heseltine has criticised the move, saying it is the equivalent of "lighting a tinder box".
The ex-deputy prime minister told the BBC talk of clawing back powers from Brussels at a time of economic crisis was "the last thing anybody wants".
Attitudes to Europe on the Conservative benches have hardened in recent weeks amid signs that EU leaders are considering closer fiscal union in response to the debt crisis crippling the eurozone.
On Monday, about 80 Conservative MPs are expected to attend the first meeting of a new umbrella group designed to air grievances over Europe and a build a platform for influencing government policy.
The gathering is designed to create a focused strategy out of different Conservative concerns and demands for action, ranging from changes to EU institutions such as the European Court of Justice, the repatriation of powers to the UK and outright withdrawal from the EU.
One of the group's convenors has said he would like to open future gatherings to Labour MPs in order to try to build a cross-party dialogue about resisting further integration.
But Lord Heseltine, one of the most pro-European members of the Thatcher and Major governments, said Conservative prime ministers were used to having to deal with "very substantial" Eurosceptic elements.
He said he "strongly" supported the stance of David Cameron, who has said the UK must focus on influencing the development of the EU and make the union "work" in British interests.
He accused those pushing for a referendum on EU membership of "opportunism", and suggested all Conservative prime ministers stretching from Harold Macmillan to John Major had pursued the same policy on Europe.
"They have all presided over a closer relationship of Britain and Europe for one reason - it is in Britain's interests," he told BBC Two's Daily Politics.
He added: "In what is an extremely fragile world situation, if you want to light the tinder box, just start saying Britain is going to start renegotiating its position in Europe.
"That is just about the last thing that anybody wants."
Speaking on the same programme, Conservative MP Nadhim Zahawi said the new umbrella group planned to discuss practical steps to boost UK sovereignty short of a referendum.
"The meeting is not about whether we should have a referendum now - that would be completely wrong and divisive," he said.
"What we are talking about is... MPs coming together to talk about, when the time is right, when Europe does fiscally consolidate, what can we do to use that opportunity to bring back powers.
"The duty of backbenchers is to do a bit of brainstorming to come up with the ideas we can actually present to the executive to say look 'these are some the ideas for a healthy relationship and settlement with Europe.'"
Meanwhile a petition urging a referendum on the UK's membership of the European Union, signed by 100,000 people including MPs and MEPs, has been handed into No 10.
The call is being backed by "dozens" of MPs - the campaign's organisers said - including Tories Philip Hollobone, Richard Shepherd, Philip Davies and Christopher Chope as well as Labour MPs Kate Hoey, Kelvin Hopkins and Roger Godsiff.
Any petition on the government's e-petitions website which gets 100,000 signatures must be considered by Parliament for a Commons debate.
It is not clear whether Thursday's petition - which has been organised both directly and online - will qualify for such consideration.
Separately, Commons leader Sir George Young refused to grant time for a debate on the repatriation of EU powers, requested on Thursday by Tory MP Priti Patel.
He said MPs had discussed, at length, European matters during the recent passage of the EU bill and there were opportunities to raise concerns in general debates and before the EU Scrutiny Committee.