A former chief constable is to head a new umbrella organisation of cannabis law reform campaign groups that will seek to change views about the use of the drug.

Tom Lloyd, formerly of Cambridgeshire police, will chair the National Cannabis Coalition (NCC), an alliance of groups calling for legal access to the drug for recreational use for adults and for medicinal use for anybody who needs it.

Lloyd has said he now regrets investigating and arresting drug users during his career as a policeman in London and Cambridge. “When you think about arresting somebody who is in possession of drugs, are you really catching a criminal?” he asked. “When it came to law enforcement I think I caused more harm than good.”

The new organisation, which incorporates groups including Norml UK, the UK Cannabis Social Clubs and the United Patients Alliance, aims to move from grassroots protests to political campaigning, targeting decision makers in UK drug policy.

“A major problem in drug law reform, and the resistance to it, is that people look at people, whether they are heroin users or stoners, and they just think they are not serious people,” Lloyd told the Guardian.

He said that traditional tactics, including the annual 4/20 day picnic in Hyde Park, were doing little to transform this perception, but many people involved in the campaign to reform cannabis laws had brought strong evidence into the debate.

“There is a deeper message and that message gets clouded and subverted by the vested interests and it’s to some extend ridiculed,” he said. “I feel that we have got the opportunity to show that we are people who are very sincere and credible, with a lot of valid information.”

The NCC’s constituent groups will still campaign on their own terms, Lloyd said, with the aim of the coalition being to coordinate efforts across the country and to reach key policymakers, whose opinions can have a big impact on official decisions.

Although the new group is still in its early days – without its own website or social media pages – it comes along at a time when the campaign to reform cannabis laws is gathering pace. Two police commissioners have recently said they will not target small-scale cannabis users and growers. Next month MPs will debate cannabis legalisation in Westminster after more than 200,000 people signed a parliamentary petition calling for reform.

Lloyd said: “The world is changing: Uruguay has now legalised it; you have got legal production in states in America; in half the states you can get medicinal cannabis. America is a very powerful player.”

Nevertheless, the government seems dead set against changing the law. The biggest challenge the group faces is transforming the narrative surrounding cannabis use. Lloyd, like many others lobbying for reform, believes this will come through the work of groups campaigning for the right to use cannabis as a medicine.

But he added: “It’s difficult to draw a line between what might be medicinal use and what becomes what we call recreational use, because anybody who wants to consume cannabis to de-stress is doing something which is probably an improvement to their health. I don’t think there is a distinction between the two.”

Jonathan Liebling, of the United Patients Alliance, which campaigns specifically on medical cannabis use, said the hope was that bringing together a range of reform groups would eliminate wasted opportunities and overlapping efforts.

Most of the alliance’s work involves lobbying MPs by urging members to write letters and turn up to surgeries, and Liebling claims a number of successes. “It’s very easy for an MP, especially a Conservative MP, to respond to an email and give you the standard party line,” he said. “But it’s much harder for them to stand in front of an MS sufferer and tell them they can’t have their medicine.”

Liebling and Lloyd will share a platform, along with Lady Meacher, a crossbench peer who chairs the All-Party Parliamentary Group for Drug Policy Reform, in London on Monday for a pre-debate public meeting on medicinal cannabis. Medicinal users of the drug will tell their stories about how it helps them to deal with their conditions.

However, there is a big omission in the list of groups constituting and supporting the NCC. Clear, Britain’s largest membership-based cannabis reform group, is not a part of the coalition, with Liebling saying that their views and tactics are not compatible.

“They don’t like the epithet ‘stoners’, they will criticise people for looking a certain way,” Liebling said. “They have separated themselves in that regard and the rest of us said you are welcome to join the NCC but you have to stop shouting at us.”

Peter Reynolds, the president of Clear’s executive committee, disputed the claim that the organisation had turned down a chance to join, saying that they had never been invited. However, he was clear that they would not sign up at this stage and added that, with more than 500,000 followers on social media, Clear was one of the UK’s biggest pressure groups on any issue.

“We have some very difficult differences of opinion with the way that the campaign ought to be run,” Reynolds said, adding that although he had respect for the work of the United Patients Alliance, he felt that other groups who sought to take their cannabis use into the street were counterproductive.

“We would unashamedly criticise anybody who behaves in that way because we feel that the new approach that we have brought to the campaign in the past five years has been proven to work. In many ways UPA is the closest to that approach, but the whole stoner, go and smoke in a policeman’s face tactic has failed.”

He added: “There is not going to be a revolution. The government is not going to stand up and say we were wrong and you are right, but we are making slow progress. I’m confident that we will have some degree of medicinal access within this parliament.”