UK government proposals to strip obese or drug-addicted welfare claimants of benefits if they refuse treatment may violate medical ethics, the president of the British Psychological Society has said.

Prof Jamie Hacker Hughes, whose organisation represents psychologists in the UK, said people should not be coerced into accepting psychological treatment and, if they were, evidence shows it would not work.

He said: “There is a major issue around consent, because as psychologists we offer interventions but everybody has got a right to accept or refuse treatment. So we have got a big concern about coercion.”

Hacker Hughes lent his voice to a chorus of criticism following the announcement of an official review to consider how best to get people suffering from obesity, drug addiction or alcoholism back into work.

A consultation paper launched on Wednesday admitted strong ethical issues were at stake, but it also questioned whether people should continue to receive benefits if they refused government-provided treatment.

In an interview with the Guardian, Hacker Hughes said claimants with obesity and addiction problems often faced complex mental health issues. But he warned the government against using sanctions to force people to accept interventions.

“It’s a problem firstly because we don’t believe people should be coerced into accepting any treatment, and secondly there is a problem because the evidence shows that if you are trying to change people’s behaviour, coercion doesn’t work,” he said.

Hacker Hughes said there was a well-documented link between joblessness and psychological problems, but said the government’s plan risked confusing the symptoms with the cause.

“It’s not just a correlational relationship, but research that’s going on at the moment shows that for every so many people who are unemployed there’s an increase in psychological problems,” he said. “Unemployment gives rise to psychological problems, so is the way to look at that to look at psychological problems or to look at causal factors?”

Commenting on the potential impact of sanctions, he added: “If you take the argument that people’s psychological problems are caused by sociological factors, and then you end up in a situation where people are worse off, it’s not going to help.”

Simon Antrobus, the chief executive of Addaction, also said he doubted that threats to remove benefits were an answer to helping people overcome their addictions.

“For people with drug and alcohol problems who are receiving welfare, benefits can provide the building blocks of recovery from addiction: regular income and access to secure accommodation,” he said.

“At Addaction we know that the people we support are more likely to recover if there is stability in their lives. This isn’t easy to achieve, so I’m not surprised that when we discussed this with our service users recently they said that a threat to remove their benefits wouldn’t be an incentive and could make their addiction worse and not better.”

Officials estimate that in August last year about 280,000 working-age benefit claimants were suffering from addiction to opiates, and 170,000 from alcohol dependency.

In addition, in May 2014, there were 7,440 working-age disability living allowance claimants whose main condition was obesity. There were also 240 claiming incapacity benefit and severe disablement allowance, and 1,540 claiming employment and support allowance.

The consultation paper published this week gave no indication of the kinds of support that would be on offer, but psychological treatment seems likely. An editorial on the issue in the British Medical Journal pointed out that the only treatment consistently successful for obesity is bariatric surgery, a major surgical procedure.

“Requiring people to undergo a major surgical procedure as a condition of receiving benefits seems far from ethical,” it said.

Jill Tipping, the director of Helping Overcome Obesity Problems, an obesity support group, welcomed any promise of help. But she said there simply wasn’t a wide enough range of services available for people with serious weight problems.

“When you have got an 18-year-old who is five stone overweight, who’s completely messed up head-wise, and needs help for food addiction, the child really needs psychological support and counselling,” she said.

“We can’t see that there is adequate treatment out there. Look at the amount of money spent on obesity, it’s a tenth of the money spent on drug and alcohol addiction. It’s a pitiful amount.”

Paul Atkinson, a London-based psychotherapist and member of the Alliance for Counselling and Psychotherapy, called the government’s proposals an outrage. “It’s the same psychology from the government of punishing rather than working with people. Under a regime like welfare and jobcentres at the moment it is going to be felt as abuse, punitive and moralistic.”