A chief constable has called for the ban on cannabis to be scrapped, arguing that it damages public safety, puts users in more danger, and gives millions of pounds to organised criminals.

Mike Barton, who leads the Durham police force, said people growing a couple of plants for personal use would not be subject to raids in his jurisdiction. Durham police are rated as outstanding in their effectiveness by the official police inspectorate.

His comments came after the former Conservative party leader William Hague last week said the war on cannabis had failed and the class-B drug should be legalised.

Barton said his experience trying to enforce the ban led him to conclude it was damaging public safety, not protecting it. “Yes, it should be legal. That’s what I think based on my experience,” he said.

“When I joined the police in Blackpool 38 years ago there was one drug squad detective; now everybody is on it. I’ve seen a remarkable deterioration in drugs in society over the last 38 years. What we are doing is not working.

“The status quo is not tenable. It’s getting worse. Drugs are getting cheaper, stronger, more readily available and more dangerous. I have come reluctantly over the years to the conclusion that we need to regulate the market. If you can regulate the market you can make sure it’s old-fashioned cannabis – not skunk or spice.”

Hague, a former foreign secretary, last week sparked a debate by saying the legal prohibition on cannabis should be scrapped. The Home Office rejected his suggestion but has ordered a review about the use of cannabis for medical reasons.

Several states in the US have decriminalised or legalised cannabis use, as have countries such as Portugal.

Barton said the moral argument used against cannabis, that legalisation would be seen as a signal encouraging people to take it up, was bogus. He said: “If someone is an adult and makes a choice to do something that does not harm anyone else, who are we to judge? People have already made that judgment – a third of people have tried it.

“The people who think cannabis should be prohibited have secured the high ground on their moral position. But if it is a plant which is freely available and a third of people have decided they want to take it, the prohibition argument has lost its efficacy. Prohibition does not work. We are creating a latter-day mafia in the UK.”

He added the ban benefited criminals, not public safety. “Organised crime is buying land and property to launder their money. That money could be paying for the care of the elderly, education, rehabilitation of drug addicts,” he said.

Barton said in his area of Durham his officers would no longer apply to magistrates for a search warrant to raid the premises of small-time cannabis growers and those caught using for personal use will be offered a place in a rehabilitation programme called Checkpoint.

Barton said: “We will not apply for search warrants for one or two plants. We want to harness our energies and focus on industrial-scale drug dealers who are damaging society.

“If you have a small amount for personal use you will not be prosecuted, you go into Checkpoint. It frees up time to investigate more serious crime – that’s why we have a good detection rate.”

Barton said a debate about cannabis legalisation was needed. “An adult should be able to have cannabis without worrying what the police are doing,” he said. “That happens in many states of the United States and other countries and civilisation does not disappear before their eyes. We need a grown-up debate. Who said in a democracy we can’t discuss things?

“Privately I know of other [police] chiefs, not the majority. More and more are saying this is crazy.”

His call for a debate was supported by Simon Kempton, the vice-treasurer of the Police Federation, which represents 120,000 rank-and-file police officers. “The Police Federation believe that it’s time to have an informed and open public debate on the future of drugs legislation incorporating health, education and enforcement programmes,” he said. “After 100 years of prohibition on the use of drugs, it’s time to ask whether this approach is working to address the issues around drug use.

“The police service must focus efforts in areas that cause the most risk and harm to the public and for some chief constables that means focusing on areas other than cannabis.”

Former Scotland Yard senior officer Brian Paddick, now a Liberal Democrat peer, said: “Legalisation will reduce the harm it causes. You can control the strength and make sure under-18s don’t get hold of it, take it out of the hands of criminals and raise considerable amounts in taxation.”