Tightening up over plumbers.
The warning was issued by the Association of Plumbing and Heating Contractors.
It said a huge intake of new plumbers into the industry has made up the shortfall of a few years ago, but the gaps have been plugged by people who don't have the experience to provide the service people should expect from a plumber.
Jan Mitman, from Drain Doctor Plumbing, said: "We have said for many years that it is not possible to teach somebody plumbing in a matter of weeks.
"We don't allow anybody to become a franchise owner without knowledge of plumbing. If they don't come from a plumbing background, we insist on them employing plumbing and drainage experts to actually carry out the work.
"The reputation of plumbers has taken a battering over recent years - even the Government has taken a swipe at the industry in the last few weeks.
"It is time plumbing companies, and individual tradesmen, worked together to rid this industry of under qualified and rogue traders."
To contact the association call 02476 472 510.