Incompetent tradesmen have cost UK homeowners an estimated £1.9 billion over the last year - five times more than domestic burglary claims over the same period, a survey suggests.
Almost one in five (17%) of the 18 million homeowners who have employed tradesmen in the last 12 months had to have at least part of the work redone at an average cost of £600, the poll for the TrustMark tradesman scheme found.
A quarter of those polled (26%) said they did not know where to find impartial information about tradesmen, with the same number saying they made a decision based on a recommendation from friends or family.
Some 6% selected a tradesman based on the cheapest quote.
The majority of homeowners (57%) who hired tradesmen to work on their home in the last 12 months said they did not check qualifications, and just 2% believed that having the best technical qualifications was the most important factor in making the choice.
Two fifths (41%) of homeowners said they were not confident in knowing where to report any problems and a third (34%) said they would not know how to get a problem resolved.
Consumer Minister Jenny Willott said the scheme was the most comprehensive set of standards to date, giving homeowners access to tradesmen who had undergone rigorous, expert checks.
Ms Willott said: "TrustMark gives consumers more confidence in their tradesman when spending their hard-earned cash.
"Every trader who has signed up to the scheme has been independently assessed for their competence.
"We want to put rogue or unscrupulous tradesmen out of business. One of the best ways to do this is to pick out the best businesses, so people know where to turn first for their home improvements, maintenance and repairs.
"I would encourage all legitimate and honest tradesmen to sign up to this scheme."
TrustMark chairwoman Liz Male said: "Something that has become increasingly apparent is that people need a reliable and trustworthy source for finding trusted and good quality local tradesmen. This is where TrustMark comes in.
"Unlike many other 'find a tradesman' schemes, TrustMark is not an advertising directory or a website that sells leads. It is a not-for-profit organisation which means that is does not make money from consumers.
"We are using these new standards to set the bar at the highest level for tradesmen, and to empower homeowners to expect the very best from the tradesmen who work in their homes."
:: ComRes surveyed 2,678 homeowners online from March 14-20.