A Tory backbencher once touted as a successor to David Cameron has called for an in/out referendum on EU membership before the next general election.
Adam Afriyie says he will table an amendment to the European Union (Referendum) Bill, bringing forward any such vote to 23 October 2014.
The bill, which in its current form would lead to a referendum in 2017, got overwhelming backing from the House of Commons in July, with all Conservative MPs voting for it.
Most Labour and Liberal Democrat MPs abstained after their leaders dismissed it as a stunt by David Cameron to placate angry backbenchers.
The bill will reach the report stage next month, and today Mr Afriyie, writing in the Mail on Sunday, said the public was "not convinced" the Prime Minister would stick to his pledge of a vote if the Conservatives win the general election.
The Windsor MP also said an early referendum would boost the party in its bid to keep their instinctive supporters from switching to Ukip.
Claiming support from "many MPs from across all the main parties", he went on: "It's in our national interest to resolve this issue as soon as possible to create the certainty and stability our country needs for the future.
"Only by setting an early date can we kick-start EU renegotiation talks and give the British people what they so clearly want - a say on our country's future with Europe.
"The political establishment are naturally hesitant but we have nothing to fear by giving people a chance to have their say, either way, on our future relationship with Europe."
A spokesman for Number 10 said Mr Cameron would not throw his support behind the amendment as he did the original bill. He said: "The PM will not let it stand," and insisted it would not be allowed to pass "in any circumstances".
And even James Wharton, the MP who sponsored the private member's bill, warned that the amendment could damage the chances of a referendum.
He said: "This amendment would make it far more difficult to navigate the challenging procedural hurdles we need to overcome and I hope its sponsors might rethink their approach.
"We need to build as broad a base of support for the bill as we can if we are to get it through Parliament and the policy of a renegotiation, followed by an in/out referendum, is the right one to do that and the right one for the country."
Speculation about Mr Afriyie's high ambitions began early this year after after three right-leaning Sunday newspapers reported a “well-organised” campaign to secure him the leadership.
His backers say his life story - as the state-educated son of Ghanaian father and an English mother, and a self-made multi-millionaire - could widen the party's appeal to voters.
At the time of the rumours Mr Afriyie - who was a frontbench spokesman in opposition but excluded from government - said: “I will never stand against David Cameron. I am 100 per cent supportive of David Cameron... There is no truth to any of it."