Foreign Secretary William Hague has reportedly said he believes Britain could "get ahead" by loosening its ties with Europe.
Offering hope to increasingly vocal eurosceptics in the Conservative Party, he said it is "certainly not career suicide" to become linked to a new group that wants a shift in the UK's relationship with Brussels.
Speaking about a more distant relationship with the EU in an interview with The Times, he said: "It's true of the euro, it could be true of more areas in future. In fact we may get ahead as a result of being outside."
Mr Hague said the creation of the eurozone without closer tax and spending rules was "always a giant mistake" and it "would stand as a monument in time to how group-think can go so seriously away from what is realistic".
David Cameron has come under increasing pressure to hold an "in out" referendum on Europe.
Earlier this week a 100,000-name petition was delivered to Downing Street, enough to trigger consideration of a parliamentary debate on the issue.
But Mr Cameron has insisted there is "no case to answer" on membership, adding: "I want us to be influential in Europe about the things that matter to our national interest - promoting the single market, pushing forward for growth, making sure we get lower energy prices."
On Monday a group of 80 new intake Tory MPs will meet to discuss what reforms they want.
Backbencher George Eustice, one of the group's conveners, said: "The aim of this new group is to promote debate about creating a new relationship with the EU and reversing the process of EU integration."