A world authority on drug abuse has called for Scotland to provide heroin on the NHS.

Swiss expert Thilo Beck added his voice to growing demands for the country's most vulnerable addicts to be treated with the help of the substance they crave.

Drugs deaths in Scotland have remained stubbornly high - just as they fall in neighbouring northern European nations that have adopted Swiss-style heroin-assisted treatment or HAT.

Dr Beck - a champion of the system based at Zurich's Arud Centre for Addiction Medicine - said be believed Scotland could save money and lives by doing the same.

He said: "I think Scotland can only win by adding HAT to its treatment offer. "It is cost effective for the public and the politicians. You save money.

"And that is not even taking account of the advantages for the users.

"So many of the users we have stabilised in HAT would have died otherwise. "It's a very important part of our treatment of opiate dependants."

Switzerland, which launched HAT in 1994, now has more than 20 clinics treating the toughest addict cases with heroin, the kind of older users who tragically tend to die in Scotland.

Germany, the Netherlands, Spain and other countries have fallen suit.

Scottish experts have been calling for such treatment since at least 1981, just a year after mass imports of heroin kicked off Glasgow's epidemic.

Until the Misuse of Drugs Act in the early 1970s, all of Scotland's handful of heroin users had been treated this way.

Labour MSP and psychiatrist Richard Simpson tried to champion a return to such practices - with heroin treatment and consumption rooms - when he was deputy justice minister before his 2002 resignation.

Dr Simpson - who worked as an addictions psychiatrist - said: "Deaths are still going up in Scotland, whereas in every other country in Europe, including England, they have been reducing significantly.

"Scotland has a particular problem. The people who are dying are older people, people for whom the treatment systems have not succeeded.

"The time has come for us to address the continuing high level of deaths by providing HAT for those adults for whom other systems have failed. It should be piloted in Glasgow."

Dr Simpson - and Dr Beck - stress that HAT isn't for all addictions. It is only for the small proportion who don't respond well to methadone or other substitution treatments that have helped stabilise tens of thousands of Scots.

The Scottish government's own drug deaths advisers have called for ministers to consider HAT, which is legal in Scotland despite its lack of political support.

Officials stress that doctors have been able to apply for licences to treat addicts with diamorphine, medical heroin, since 2012. None have. Drugs activists stress that strong signals of support from ministers would be needed before NHS doctors did so. Such signals have not been made.

The Scottish Drugs Forum has lobbied for such changes for more than a decade. Dave Liddell, its director, said: "With a large proportion of the most vulnerable problem drug users being out of treatment and at high risk of dying through drug over dose it is vital that we explore ways to encourage the most hard to engage with drug users into services.

"There is now a substantial evidence base around HAT and its positive benefits for the individual and wider society and we would support its introduction as a useful addition to the spectrum of services in Scotland."

A Scottish Government spokeswoman said: "We are continuing to tackle the damaging impact of drugs and making recovery a reality for individuals, families, and communities affected through our national drugs strategy, the Road to Recovery."