Six weeks ago Jack McConnell drove to a farmhouse in South Lanarkshire to visit six female heroin addicts undergoing a controversial withdrawal treatment.

Yesterday, the First Minister welcomed the same women into his official residence in Edinburgh, Bute House, and found them transformed.

He embraced Elizabeth Wilson, 27, a mother of three, who had been a heroin user for 10 years. She spent six of those years on the methadone programme, but never succeeded in quitting heroin.

"If you don't mind me saying, you're in remarkably good shape compared to the last time I saw you," Mr McConnell said.

"I feel like I've never used drugs in my life," replied Mrs Wilson. "I've had no cravings at all, ever since I did NET."

NET stands for neuro-electric therapy - a type of drug detoxification treatment, invented in the seventies by a Scottish surgeon, Dr Meg Patterson.

The creators of NET want to use it to help Scotland's 51,000 heroin addicts kick their habit and to reduce the country's reliance on the methadone programme.

Yesterday, they handed Mr McConnell a proposal to carry out three full clinical trials of NET, one of them in a Scottish prison. The First Minister, visibly moved by the addicts' recovery, promised to do "everything in my power" to make sure that trial takes place.

In a frank discussion, he admitted Scotland's prisons are failing to deal with drug addiction, with the consequent reoffending by addicts released into the community.

He also vented anger at local authority care services for failing to provide a residential facility for women who want to quit drugs. He promised to make it his duty to see such a centre is built.

"When I visited these women undergoing NET, I spent time with each of them individually. I talked to them about their lives and their previous attempts to become drug free.

"There is something wrong in Scotland, when indecision in the services meant to help people get off drugs, has led to a position where there are no residential rehab places for women.

"These women need somewhere to go. They need to make a decisive break from their communities where, often, their friends and their families are taking drugs. I feel a deep sense of frustration such a facility doesn't exist.

"If it's not going to happen by local decision making, then we need to make it happen by national decision making."

In the trial, six men and six women underwent a seven-day course of NET - a drug-free treatment, whereby a weak electric current is applied to the addict's brain.

Six weeks later, four of the women are still drug-free, as are four of the men - a success rate far greater than conventional heroin addiction treatment.

They include Sharon Hamill, 45, from Irvine, a mother of three, who had been a heroin user for six years.

"If it wasn't for this treatment, I would be dead by now," she told Mr McConnell.

"I had two draws six years ago and I've been battling it ever since. My children watched their mother turn from a caring Christian into a wreck.

"I've tried cold turkey 12 times and failed every attempt - I could never get past the cravings. I tried methadone - it stopped me withdrawing but it could never replace the rush. But since NET, I haven't had a single craving."

Glen Keys, 39, had been using heroin for 15 years, eight of those on methadone. He took 90ml a day, but it was never enough to stop him using heroin.

Yesterday, he was there with his wife, Debbie. "The change in Glen has been incredible," she said. "My wee girl said to me last week - what's up with Daddy? How come he's laughing so much?"

The First Minister said he was moved by the change he had seen.

"When I saw the women going through treatment they were so fragile. Today, they are looking so healthy, so confident. They are even applying for jobs. The signal about NET is very positive.

"I'm in no doubt now there is a case for further research. I have encouraged officials in the health department to work with the creators of NET to put together a realistic research proposal. I will continue to do everything I can to make that happen."

Scotland has more drug addicts per head of population than any other country in western Europe. There are around 51,000 heroin addicts, about 20,000 of whom are on methadone.

Experts believe methadone works - and is much cheaper than letting addicts turn to crime to feed a heroin habit. But, the majority remain heroin users, according to research by Professor Neil McKeganey, of the Centre for Drug Misuse Research, who monitored the recent NET trial.

McKeganey is in contact with more than 1000 heroin addicts across Scotland.

After three years of methadone use, only 3% of addicts had given up heroin. While methadone may reduce withdrawal symptoms, it doesn't provide the buzz that heroin does.

Despite this, Scotland spent more than £4m on methadone prescriptions between 2002 and 2003. The total cost of the programme could be as high as £12m a year, says McKeganey.

Meanwhile, between 10,000 and 20,000 people are becoming hooked each year.

In the light of these figures, drug-addiction charities and campaigners are calling for new approaches based around abstinence, instead of methadone.

NET is one such treatment. During "cold turkey", patients wear a small battery-powered device, which applies a weak electric current to the brain.

The treatment, which lasts seven days, is said to alleviate the withdrawal symptoms and remove the cravings for the drug.

Early trials of NET yielded drug-free behaviour for 80% of the participants, when combined with two weeks of residential care. But there are lingering doubts about how NET works and whether the treatment is any more than a placebo.

Although NET has been used to successfully treat thousands of drug addicts over three decades, its creators have never been awarded a grant to stage a full medical trial. That may be about to change.

Yesterday, Seaboard Companies, which owns the patent for the NET device, handed a proposal to the First Minister for a full clinical trial of NET, involving 600 addicts, in Glasgow.

They have also spoken to the governors of two Scottish prisons, about a plan to stage a trial of NET within a jail, involving up to 400 addicts.