Most cannabis users caught by police will in future escape with a warning and confiscation of the drug.
Most cannabis users will not now face arrest
Under new police guidelines, cannabis users will only be arrested in certain aggravating circumstances.
These could include smoking in public, having the drug around children or for being persistent offenders.
But critics say the new rules will cause widespread confusion, with many mistakenly thinking the drug has been made legal.
And mental health campaigners were concerned they would send out the message that cannabis was risk-free.
The guidance does not specify an amount users can claim is for their own consumption.
But anyone under 17 found using cannabis will still be arrested, under the guidelines drawn up by the Association of Chief Police Officers (Acpo).
Officers dealing with cannabis possession will still be required to record the incident as a crime.
And users will still be arrested in areas where local residents have complained.
The guidelines apply to police forces in England, Wales and Northern Ireland.
CANNABIS AND THE LAW
Cannabis is due to be downgraded from a category B to a category C drug in January
From then on, people will not usually be arrested for possession
But it will remain an illegal substance
Some circumstances could still lead to arrest - for instance smoking in public, having the drug around children or for being habitual users
Under-17s using cannabis will still be arrested
Maximum sentence for dealing will remain 14 years
They will be implemented early next year, when cannabis is expected to be reclassified from a category B to a category C drug.
Government ministers and police chiefs said the guidelines would allow officers to concentrate on dealers, and on more harmful drugs such and heroin and cocaine.
"I think that's an important message to get out there," said Caroline Flint MP, the Home Office's drugs spokeswoman.
"People who deal in drugs, whether it's cannabis, or crack cocaine or ecstasy... these are serious crimes against individuals and our communities and they will be penalised heavily."
Heroin and crack
Acpo said there was no evidence that the relaxed guidelines might encourage teenagers to smoke cannabis or try harder drugs.
"The theory of 'gateway drugs', i.e., someone starts with cannabis and then might migrate onto a more serious drug, does not stand up," said Acpo's drugs spokesman Andy Hayman.
Drug reform group Transform said a total legalisation of cannabis would be preferable.
And Shadow Home Secretary Oliver Letwin attacked the proposals as the "worst of both worlds" destined to cause mass confusion.
"There is a case for legalisation, and there is a case for people getting off
drugs. What there is not a case for is making them semi-legal," he said.
This view was echoed by Adfam, a charity working with families affected by drugs and alcohol.
Its chief executive, Vivienne Evans, said: "If there is confusion over the law concerning cannabis, this could add to the misunderstanding of the impact that cannabis use can have within a family."
North West Euro MP Chris Davies, who was fined in 2001 for possessing cannabis during a campaign to legalise the drug, said he was alarmed that the maximum sentence for dealing the drug would remain 14 years.
"If dealers are going to face 14 years in prison for the supply of cannabis,
there is no incentive not to sell other drugs as well," he said.
"Cannabis users may be
pushed into the hands of heroin dealers."
Marjorie Wallace, chief executive of the mental health charity Sane, said the government needed to remind people the drug was not "risk free".
"For those prone to severe mental illness, particularly young people, using cannabis can provide the fatal trigger to lifelong illness and risk of suicide," she said.
However, one representative of cannabis users, Star, of the Tribal Voice Shop in Plymouth, welcomed the new rules as a "brilliant idea".
"It will free up more police resources for tackling harder drugs such as cocaine and heroin.
"Also it will let the police have more time to deal with inner-city crimes like muggings and mobile phone thefts."