Tories need to connect with liberal youth or risk being reduced to rump party in rural England, warns Nick Boles

The Conservatives risk being reduced to a rump party in rural and suburban southern England unless it is able to reach out to liberal-minded younger voters, a close ally of David Cameron warned today.

Nick Boles, the Planning Minister, attacked the willingness of some Tory MPs since the Coalition’s creation to play along with the caricature that the party contained “heartless extremists”.

His outspoken remarks dismayed senior Conservatives who moved swiftly to distance themselves from the comments.

Mr Boles, an early supporter of Mr Cameron’s pledge to modernise the party, called shortly after the Coalition’s formation for a pact between the Conservatives and Liberal Democrats at the 2015 election.

In a speech today Mr Boles explained that he had believed a pact would have been the best way to achieve the “broad, open and generous party of my dreams”, but now he realised he had been misguided.

He said: “I thought our willingness to compromise with the Liberal Democrats in the national interest would help persuade the public that we moderated our ideological fixations, would show we had really changed.

“I did not realise our coalition partners would do everything in their power to paint us as heartless extremists. And I underestimated the readiness of some in the Conservative party, and the press, to play up to the caricature and thereby fall squarely into their trap.”

He told the Bright Blue think-tank that the Tories now had to be “our own liberals” to ensure they did not reverse the “fragile gains of modernisation”.

Mr Boles said voters under 25 were “markedly more liberal on both social and economic issues” than their older relatives – and his party had to realise they would respond to a different message from that aimed at “stalwart supporters”.

He said: “The Conservative Party will only rebuild itself as a national party which can win majorities on its own if it understands it cannot do so by making a single undifferentiated pitch to every age group and in every part of the country.

“If we are to avoid being pushed back into a rural and suburban redoubt in the south of England, we need to redefine ourselves as an alliance of distinctive political forces which work together to produce a common election platform and programme of government.”

Mr Boles floated the idea of reviving the National Liberal Party, which existed between 1931 and 1968, when it merged into the Conservative Party. He suggested it could field joint candidates with the Tories to maximise support – particularly in three-way marginals where the Liberal Democrats perform strongly.

“We could use it to recruit new supporters who might initially balk at the idea of calling themselves Conservative,” he added.

A senior Tory source slapped down the idea, saying: “We will field Conservative-only candidates at the next election. Nick Boles is speaking for himself, not anyone at No 10 or Conservative Campaign headquarters.”

A Liberal Democrat source said: “We understand Nick Boles’ frustration with some elements of his own party. But if he’s looking for a sensible party of the centre ground, he’s welcome to apply to join the Lib Dems.”

Jon Ashworth, the shadow Cabinet Office Minister, said: “Nick Boles, one of the Prime Minister’s closest advisers, has let the cat out of the bag – David Cameron’s so-called detoxification of the Tories has been a sham and his modernisation project is dead and buried.”