Dr Gabor Maté, a retired physician who worked in a similar facility in Vancouver, said blocking the facility was “pure political opportunism”.
Drug consumption rooms allow users to inject in safe and sterile surroundings.
The opening of such a facility in Glasgow has the backing of the health board and the Scottish Government, but the issue of drug control is reserved to Westminster. Last year the UK government refused a request from Glasgow City Council amid legal concerns.
Dr Maté, author of In the Realm of Hungry Ghosts, a book about tackling addiction, said concerns over legislation were a “cop out”.
He said: “It’s just an excuse – the government can change the law. We know that harm reduction works. Until it was overwhelmed by the fentanyl crisis, the supervised injection site in Vancouver worked: there was less transmission of disease, fewer health expenses for society. There was benefit all around with no downside whatsoever.
“In Britain, there has been a history of heroin clinics. They were successful: there was less crime, more employability, better relationships.
“All the evidence is in. The arguments against are pure political opportunism. No politician ever loses votes by being tough on drug addicts.”
Research published earlier this year in The Lancet said factors such as homelessness and cocaine injecting had helped create a “perfect storm” in Glasgow, with over 10 per cent of intravenous drug users in the city centre now infected with HIV, compared with just 1 per cent a few years ago.
The study found a large population of people who inject in public places, with an increase in cocaine use possibly the result of declining heroin purity.