The Government is to reject recommendations from a high-powered group of advisers who believe it should stay a "soft" drug.

The Prime Minister is believed to regard the move as crucial for sending a clear message to young people that cannabis is harmful and linked to serious crime.

A final report from the Advisory Council on the Misuse of Drugs (ACMD) is being delivered to the Home Office - although the Government's response will not be announced until next week at the earliest.

The experts - including doctors, police, judges and drug counsellors - are understood to have concluded that cannabis should remain in the Class C category.

However, Whitehall sources indicated that Mr Brown was determined to push through reclassification to Class B.

Going against the ACMD's decision could spark a massive row and trigger resignations from the committee, which plays a crucial role in setting Britain's drug policy.

Liberal Democrat home affairs spokesman Chris Huhne demanded that the panel's recommendations be published.

"The Government must stop playing politics and publish this advice as soon as possible. There should be nothing secret about the scientific advice being given to ministers on this important issue," he said.

Official data revealed earlier this year showed abuse of highly-potent "skunk" cannabis has escalated in the past six years with the drug now dominating the cannabis market in England and Wales.