Strict lending criteria for residential properties affected by Japanese knotweed should help to control the problem within 22 years, data shows.

Mortgage lenders will only offer loans on properties affected by knotweed if a professional treatment plan is in place with an insurance backed guarantee lasting five or 10 years, according to research by Environet UK.

If the knotweed returns after treatment has been completed, further treatment will take place to protect the property and loan.

Sellers are legally-obliged to disclose the presence of knotweed, when completing the Law Society’s TA6 Conveyancing Form, even if a property is bought without a mortgage.

If sellers are unaware of the presence of knotweed, surveyors should pick it up in their survey and order a treatment plan to be put in place before the sale proceeds.

‘Huge backlog’

Nic Seal, founder and managing director of Environet, said that the problem of Japanese knotweed has only been confronted by lenders in the last decade, meaning firms are still dealing with a huge backlog of affected properties.

He added: “Around 4.5% of UK properties come to market every year which means that, by 2040, the vast majority of UK housing stock will have been sold at least once and any knotweed infestations should have been tackled.

“While new cases of knotweed will of course arise in that time, and knotweed will continue to encroach on our homes from public land, railways and road sides, the rapid spread of the weed across the UK will be under control by that point.”

According to the figures released in September 2018, Japanese knotweed wiped £20bn off the value of the property market in the UK.