Opal has been chemically engineered so that it does not give sniffers a 'high' when inhaled, enabling addicts to kick their habit. Young men and women who until recently spent much of their time sniffing on tins and bottles filled with petrol are now returning to school, applying for jobs and recovering their health.

'It's made a dramatic difference,' said Alison Anderson, an Aboriginal MP whose constituency covers 35,000 sq km of desert between Western Australia and Queensland.

'You don't see kids sniffing any more in places like Kintore, Papunya and Docker River. It's a combination of Opal and a lot of hard work by community groups and Aboriginal people themselves.'

The number of regular petrol sniffers in the Northern Territory has dropped from about 600 to just 20 since Opal was introduced to more than 60 settlements two years ago.

In the vast Anangu Pitjantjatjara Yankunytjatjara Aboriginal reserve in South Australia, where petrol sniffing was endemic, there has been an 80 per cent drop in the number of sniffers in two years.

'The crisis has passed,' said Tristan Ray, the co-ordinator of a petrol-sniffing prevention programme in remote indigenous communities. 'But it's a window of opportunity, not a permanent situation.

'The underlying causes of petrol sniffing - boredom, lack of opportunity - are still there. We need to get kids back into school, give them better recreational activities and improve things like childhood nutrition.'

Opal became available in Alice Springs, by far the largest town in the Outback, in September. Petrol pumps bear the words 'Opal - a safer petrol for remote communities'.

But regular petrol is still for sale, and there are at least 20 hardcore sniffers living in the squalid Aboriginal camps which lie scattered around the desert town.

To eliminate the problem, Alice Springs would need to switch entirely to Opal.

That is impossible for now because some new and high-performance vehicles require high-octane premium fuel.

'We've always said that Opal is only one part of the solution,' said BP spokesman Chandran Vigneswaran. 'It's had a positive impact but it needs to be combined with other measures such as providing diversionary activities like sport for Aboriginal people.'

Some drivers have complained that Opal is a less efficient fuel, but BP insists it performs just as well as regular unleaded petrol. 'In some cases it performs better than unleaded,' said Mr Vigneswaran. 'It won't damage vehicles at all.'

More than 100 people have died from petrol sniffing since the 1980s, according to a study released last year by analysis agency Access Economics. It estimated petrol sniffing has cost Australian taxpayers A$79 million through the expense of dealing with crimes committed by addicts and the added burden to the health-care system.

Access Economics found that three-quarters of adult disabilities among Aborigines in the remote Western Desert were a result of petrol sniffing. Young Aboriginal women were selling themselves for sex in exchange for cans of smuggled petrol. Two-thirds of female sniffers were infected with sexually transmitted diseases.

The challenge is to ensure that bored and disaffected young Aborigines do not resort to other forms of substance abuse.