Under-18s are helping to pick the next Tory leader and prime minister, despite the party refusing to let them vote in general elections, sparking accusations of hypocrisy.

Labour and the Liberal Democrats have attacked the Conservatives for allowing youngsters as young as 15 to take part in the leadership race – while refusing to lower the voting age for the public to 16.

Cat Smith, Labour's voter engagement spokeswoman, told the Politics Home website: “It is hypocrisy for the Tory government to claim 16- and 17-year-olds aren’t mature enough to vote in elections, but not apply this rule to its own leadership contest.

“If young Tories can be trusted to choose our next prime minister, then there is no logical reason why all 16- and 17-year-olds can’t have their say in the future of their country in a general election.

And Layla Moran, the Lib Dems' spokeswoman for young people, said: “The Tories will allow under-18s to choose the next prime minister, but they won’t allow them to choose their government or their own MP or whether or not they wanted to remain or leave the EU.”

“Younger people deserve a chance to have a say in their futures and to shape our society. They shouldn’t only be allowed to vote for Jeremy Hunt or Boris Johnson.”

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The Conservatives offer membership to people aged under 23 for just £5 a year – with “full voting rights” given to any members aged 15 or over.

And Mr Hunt's campaign meanwhile published a video featuring a 17-year-old Conservative member who had cast his vote in the leadership race to “battle that stereotype that our age group are uninformed”.

A string of local Tory websites say that there is “no upper or lower age limit on membership, although children under the age of 15 cannot be enrolled as full voting members”.

A cross-party bill to lower the UK voting age failed in the Commons in 2017 after Tory MPs were accused of talking it out and successive Conservative prime ministers have spoken out against change.

That year, Theresa May said: “You have to pick a point at which you think it is right for the voting age to be. I continue to think it is right for it to be 18.”

And, last year, her de-facto deputy, David Lidington, told MPs that under-18s lacked the “maturity and responsibility” required to vote.

Critics have pointed out that teenagers overwhelmingly oppose the Conservatives – particularly since the Brexit referendum.