Health and Safety Executive inspectors have launched a crackdown on rogue gas fitters.
They are warning people only to use registered installers.
It comes after Kevin Barrett, 45, of Ferndale Road, was ordered to do 200 hours community service and pay £867 in costs for carrying out work he was not qualified to do.
Barrett, pictured below, installed a combi boiler, removed an old gas boiler and fitted a cooker hob in spite of the fact that he was not registered with the Council for Registered Gas Installers (CORGI).
His botched work left the homeowner with no heater for more than two weeks and left a gas pipe improperly sealed, which could have caused a potential gas leak.
The boiler was immediately turned off by another gas fitter as soon as he saw it was dangerous.
Barrett had signed to say that he would cease gas work a number of years previously.
He was charged with breaches of falsely pretending to be a member of CORGI and undertaking work while not being a member of CORGI.
"Unfortunately there are many people working on gas appliances who are not registered," HSE principal inspector Nigel Long said.
"We are working to identify them and to take the necessary enforcement action.
"However, the customer also has a role to play. They need to check that anyone they ask to do gas work is CORGI registered."
Genuine registered installers carry a photo ID and their details can be checked with Corgi by calling 0870 4012300.
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