David Cameron is today urged by Tory modernisers to abandon Britain’s 40-year “futile” war against drugs and make partial legalisation a key pledge in next year’s general election manifesto.

The provocative plan is contained among a series of policy proposals put forward by the influential Conservative think-tank Bright Blue, a group which is backed by senior ministers including Theresa May, Francis Maude, and the former minister Andrew Mitchell.

It suggests that drug reform would appeal to young and ethnic-minority voters, who are crucial to the party’s long-term survival, while saving millions of pounds of public money.

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Other controversial policies put forward in The Modernisers’ Manifesto include abolishing universal winter fuel payments and excluding students and highly skilled workers from the Government’s net migration target. It also suggests introducing a requirement for new teachers to have at least a 2:1 degree in core subjects and abandoning automatic pay rises for doctors and nurses.

But it is likely to be the proposal for decriminalising drugs – put forward by the journalist and former Cameron adviser Ian Birrell – that will prove most controversial. In his article for the manifesto, which is reproduced by The Independent today, he reveals that Mr Cameron briefly flirted with the policy after becoming Tory leader in 2005. He said it was abandoned because of the fear of “hostile headlines”.

But Mr Birrell, a former Deputy Editor of The Independent, said changes since then had made the cause of decriminalisation right and electorally advantageous. He cites a recent poll that found a majority of people favour permitting cannabis use, while four in 10 Britons favour total decriminalisation. “It is hard to think of another policy with the same potential to challenge popular conceptions of conservatism,” he writes.

While the policy is unlikely to find favour with Ms May and others on the Tory right it does reflect a growing international trend following the legalisation of cannabis in some US states. The Liberal Democrats have already said they will set up a Royal Commission to overhaul Britain’s drugs rules and some within Labour would back a similar approach.

Ryan Shorthouse, director of Bright Blue, said it was important for the Conservative modernisers to engage in this debate as well.

“What is clear is that much more needs to be done on the development of drugs policy in the UK as the current situation is both economically and socially damaging,” he said.

“We believe that the Conservatives at the next election need to be seen to be taking on the big, difficult issues facing society and not be distracted by the Ukip agenda of Europe and immigration.”

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Mr Shorthouse said Bright Blue would not go as far as Mr Birrell in advocating the complete legalisation of drugs but partial decriminalisation needed to be looked at.

Tory modernisation: What is Bright Blue?

Bright Blue is a Conservative think-tank that was set up in 2010 to keep alive the flame of Tory modernisation in government. While not specifically linked to any wing of the party, its ideas tend to be relatively liberal and several key Tory modernisers such as David Willetts and Francis Maude are on its advisory board. Those connected with the group are concerned that too much focus on immigration and Europe, to combat the Ukip threat, will alienate centrist voters and could deprive the party of victory next year.