A study by the French environmental campaigning group Robin des Bois found that a typical two-hour barbecue can release the same level of dioxins as up to 220,000 cigarettes.

Dioxins are a group of chemicals known to increase the likelihood of cancer.

The figures were based on grilling four large steaks, four turkey cuts and eight large sausages.

This amount of cooking was found to release 12-22 nannograms of dioxins into the atmosphere.

The researchers also found that the average concentrations of dioxins in the vicinity of the barbecue ranged from 0.6 to 0.7 nannograms per cubic metre – up to seven times higher than the level authorised for public incinerators at the point of discharge from the chimney.

Food

The French food safety agency is also undertaking research into the possible cancer-causing effect of carbonising food during the barbecuing process.

They have found that some hydrocarbons which have been linked to cancer are incorporated into the food.

Desmond Hammerton, a retired professor of Marine Biology, is campaigning to raise awareness of the problem.

He called for warnings to be included on barbecue equipment.

He said: ‘I’m sure that just the odd barbecue during the summer is not going to have any effect.

‘But if you have a barbecue once or twice a week through the summer, and all crowd round it and inhale the fumes then over 10 or 20 years maybe that would do something.’

Research published by the Food Standards Agency shows that the average intake of dioxins and dioxin-like chemicals called PCBs in the diet has fallen by 50% between 1997 and 2001.