The government's drug's policy threatens schoolchildren and is driven by a "liberal elite", the Conservatives have warned.

During a Commons debate on drugs policy, shadow home affairs minister, Nick Hawkins, rounded on David Blunkett's recent reclassification of cannabis to a grade C drug.

The Surrey MP highlighted three studies linking cannabis to "huge increases" in depression or schizophrenia and a five-fold cancer risk.

By liberalising the drug, Hawkins claimed that ministers were sending the wrong signal to children.

He accused the government of listening to pro-legalisation "crackpots on the Labour backbenches".

"The physical and mental health of a whole generation of youngsters is being put at risk because of this government's willingness to accept the drugs agenda of a small liberal metropolitan elite," he said.

Home Office anti-drugs minister, Bob Ainsworth, asked Hawkins whether a Tory government would reverse the move?

After citing scientific research showing cannabis dangers, the Conservative frontbencher said his party would take a different approach.

"We have said that when we come to office any changes we make will be evidence based," he told MPs. "We actually believe in science."

"We will try to do everything evidence based not based on the pro-legalisation fantasies that are shared by a number of his backbenchers."

While the Conservatives have yet to take an official line on overturning cannabis reclassification other frontbenchers have taken a hawkish line.

"I think David Blunkett has made a mistake and I would be astonished if when we return to government we stick to the policy that he introduced this last week," the former home secretary and shadow chancellor, Michael Howard said recently.