Mr Davis has pledged to reverse Labour's reclassification of cannabis

The Haltemprice and Howden MP said the government's move had wrongly persuaded people cannabis was safe and legal.

"We have opposed this lunacy and we will reverse it," he said.

Speaking at the Tory party's spring conference in Harrogate, Mr Davis said it would be his first move as home secretary.

He said drug related crime cost the country �25bn a year and the government had a responsibility to stop young people starting on "the path to self destruction".

'Shaky grasp'

"Some people say we've lost the war on drugs. But Labour haven't even begun to fight it," he said.

Under a Tory government, drug addicts would be given the choice of residential treatment or the criminal justice system.

But Labour's drug minister Caroline Flint questioned where the money would come from to pay for residential programmes when the Conservatives are proposing to freeze the Home Office budget.

"Now David Davis is admitting that his first action as home secretary would be to tell the police to stop focusing their efforts on the Class A drugs that destroy lives and communities," she said.

"Not for the first time, he has shown a shaky grasp of his brief."