THE debate over whether cannabis should be made legal has returned once again as a cross party group of MPs have backed calls in favour of it.

Former deputy prime minster Nick Clegg and former health minister Norman Lamb joined Labour and Tory figures to back a new report which claimed legalisation could net the Treasury more than £1 billion a year in tax revenue.

The Adam Smith Institute and Volteface study argued that the UK should follow the lead of the United States, where four further states legalised marijuana in this month's elections.

It came as Germany gets ready to legalise cannabis for medical purposes and Canada prepares for all-out decriminalisation.

The report argued that Britain's "dark ages" drugs policy has failed to stop people drugs being manufactured and used, and to stop associated crime, corruption and killing.

The number of offenders in prison for cannabis-related offences in England and Wales would also likely drop from the current 1,363, who cost taxpayers £50 million a year, the report said.

Mr Clegg said: "British politicians need to open their eyes to what is happening in the rest of the world.

"Cannabis prohibition is being swept away on a tide of popular opinion and replaced with responsible legal regulation.

"Now is the time for ministers to start writing the rules for this legal market, including age limits and health warnings, so that we can finally take back control from the criminal gangs."