- Published on Wednesday, 28 September 2011 15:56
Seventy-nine per cent of boilers installed by 'cowboy' firms in the capital were deemed a risk or "immediately dangerous".
Gas Safe Registre urged homeowners to use qualified fitters and report those trading illegally.
The warning comes as the Department of Health revealed that large numbers of people are being treated in hospital for low-level carbon monoxide poisoning. Over a year, accidental carbon monoxide poising led to more than 50 deaths as 4000 people were hospitalised.
GSR, which monitors gas fitters, says there are about 7,500 cowboys nationwide who do 250,000 illegal jobs a year. It says Londoners are more at risk from dangerous boiler installations than anywhere else in the country.
Ross McTaggart, GSR's head of field operations, said "We need to stop these people and the only way to do it is with the help of the consumer."
"These trades are putting people's lives in danger. The primary issue arising from illegal fittings is carbon monoxide poisoning but a boiler installed illegally can also cause explosions or fires. We need to raise awareness of this and urge people to make sure they check a fitter's credentials."
As part of Gas Safety Week GSP is urging Londoners to report rogue trades and make sure they hire qualified engineers who carry a Gas Safe ID card.
West Dulwich resident Marcia Morgan had a huge gas leak in her home after rogue builders installed the wrong kind of boiler in 2008.
The freelance stylist called in a gas inspector this year. She said: "I was horrified when he immediately swiched off the boiler saying it could have blown the side of my house off."
Ms Morgan added: "My builder appeared to have the right credentials but he obviously wasn't qualified"