Consumers have been warned against illegal gas fitters, as gas-related accidents could impact on home insurance premiums.
According to the Gas Safe Register, fixing botched illegal gas jobs is costing consumers £100 million a year. Illegal gas fitters are also putting life and property at risk.
The register said 250,000 illegal jobs are conducted annually, and many of those inspected are found to be hazardous.
The Gas Safe Register is urging customers to check the fitters recommended by family and friends have the right qualifications.
Phill Brewster, national investigations manager at the Gas Safe Register, said: "If you have a boiler fitted by a gas engineer who isn't registered to do the work, then you may end up paying to have it ripped out and start again which may cost you thousands of pounds. It may also put your life in danger."
A survey showed that one in three people would trust a tradesman on recommendation alone. Mr Brewster is calling on people to ensure fitters are registered to work legally.
He added: "Money may be tight so it's understandable that people ask around for recommendations in the hope of getting a good job done."
© Press Association 2010