As part of its battle against rogue builders, NFB will underwrite the full cost of building repair work under the Benchmark Builder guarantee scheme, which is exclusive to the trade organisation's members. It represents more than 720 reputable contractors and builders in the region, and has strict membership criteria covering workmanship, financial status, health and safety, and a binding code of conduct.

Gary Amer, regional manager of the NFB's Southern Business Centre, said: "Many companies are their own worst enemy, and make the mistake of calling in a cowboy builder for cash-in-hand jobs thinking they're saving money on VAT.

"When things go wrong, repair work can be very expensive."

For more information, and a list of registered builders, contact the National Federation of Builders on 020 7608 5164.