Doorstep selling of double-glazing, gas and electricity and other goods has reached a value of £4.7bn a year, according to a new study from the Office of Fair Trading.
The volume of sales has been rising at a rate of 2.9% annually, led by double-glazing, conservatories and cleaning products, as firms bypass the High Street and take advantage of the opportunity to sell direct - sometimes at high prices.
The OFT says that tighter rules governing cooling-off periods and written quotes have saved consumers millions of pounds over the past few years.
But the study, compiled by a research firm GHK, highlights concerns about high pressure sales techniques in some areas, including home repairs and mobility devices for the disabled.
It adds that some prices are nearly double the best quotes and that too many buyers fail to compare prices when buying on the doorstep.