Tarquin Purdie, Founder and CEO of HaMuch.com, said: “Knotweed is a homeowner’s worst nightmare and there really is no DIY fix for this aggressive backyard vandal.
“It can take months on end to ensure it has been properly disposed of but can be more costly should you decide to turn a blind eye.
“The quicker you can get on top of the problem, the better, as a house with knotweed will not only drop in value but will also struggle to find a buyer.”
HaMuch.com’s study found higher value houses are at risk of losing more money.
In the South East of England, house prices could fall by £32,664, followed by the East of England at £29,128, and the South West with £25,976.