The stock market is faltering and house prices are on the edge of a precipice. Could cannabis smokers be the unlikely saviours of the British economy?

A major new study is being used to advise well known household and high-street companies about the gains and losses they face as cannabis smoking becomes commonplace.

Research has revealed that Britain's 'cannabis economy' is worth £5 billion a year in sales alone.

Now it has been discovered that a further £6bn of consumer expenditure each year is closely linked to the growing cannabis-users' market.

'Young people between 15 and 30 are very trend-conscious and aspirational,' said Andy Davidson, who commissioned the study for The Research Business International, trend analysts who tracked the spending habits of young people for six months.The study found that cannabis users spend an average of £20 on products that accompany their drug use each time they smoke.

Because smoking cannabis heightens appetite, users are providing a £120 million weekly windfall to a string of takeaway food suppliers, such as Domino and Pizza Hut, and manufacturers of 'munchie' products such as Mars bars and Haribo jellies.

Video suppliers and manufacturers of home entertainments such as PlayStation and Nintendo GameCube are also benefiting from the need of a generation of users to keep themselves occupied at home while their drug of choice remains unlawful.

'Some of these brands benefit at the moment,' said Davidson, 'but if people become more willing to smoke in public when the law is relaxed next year, they may be hit.'

The Government has announced that cannabis will be 'downgraded' to a class C drug next summer making arrest and prosecution for possession less likely. The move follows a controversial experiment in Lambeth, south London, where police attention focused on hard drug users and suppliers rather than cannabis smokers.

'Cannabis users also have discretionary expenditure of tens of millions of pounds each week on places to meet and eat,' said Davidson. 'They don't like shiny, noisy environments with lots of choices such as McDonald's. On the whole, they prefer somewhere with low-key lighting and a straightforward menu.

'And they don't like venues solely devoted to heavy drinking. That doesn't mean that they won't still go out for a big night once a week, but they avoid the sort of pubs that have heavy bouncers on the door.' Many cannabis users also avoid high alcohol drinks, even strong lagers.

'Thursday is now my biggest night,' reported a 22-year old woman from London. 'I hate Saturday, it's full of idiots, it's expensive. That's when I love to stay at home and smoke [cannabis].'

'I don't visit big chain bars any more,' said Anthony Green, a student from Leicester. 'They're very intolerant of anything that's outside their obvious remit of drinking and pulling.

'When we use cannabis at home, there are some things we always consume at the same time. Red Bull or smoothies, for example, and takeaway food. There's a sort of conspiracy between consumers and retailers nowadays. You know why you buy these things and they know why you're buying these things, but no one says anything.'

Drug use may even affect radio and TV scheduling in future, the research suggests. A typical 24-year old male admitted: 'I've started taking much more interest in the Discovery Channel. Cannabis really gets you thinking deeply about things.'

Government research has already confirmed that more than 15 million people in Britain have tried cannabis. There are six million regular users, more people than attend church, play Sunday league football or go jogging. TRBI's Project Edge is the first study which has openly monitored cannabis use for commercial, rather than medical, purposes.

Tobacco companies have worked secretly for years on trials of cannabis cigarettes, in spite of the fact that their scientists working on the projects risk arrest for drug possession.

However, manufacturers such as Imperial Tobacco still insist that their 'King Size' Rizla cigarette papers are intended solely for making handmade cigarettes rather than rolling joints.

Carl Ratcliff of advertising agency TBWA said: 'As cannabis gets closer to decriminalisation, you'll see more brands recognising that through their advertising. It won't be explicit, but will be heavily implicit in terms of the signs and symbols that they use.'

'It's no longer a moral issue,' said Davidson. 'Businesses targeting the youth market can no longer ignore the fact that almost half of their customer base is getting stoned every day. They need to make specific projections about how that affects them.'