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MPs say Japanese knotweed plant rules are 'over-cautious'


Following a one-off inquiry, the government’s Science and Technology Committee said the 'seven-metre rule' (the danger zone from Japanese knotweed used to decide mortgages) is 'over-cautious' and should be updated this year. 

MPs say that Japanese knotweed rule wipes thousands off the value of homes, citing one person who reported the weed had reduced their £340,000 house to a value of 'zero'. 

Some lenders refuse mortgages or make strict requirements if the weed is within a seven-metre distance of a 'habitable space', including conservatories and garages.

According to The Telegraph, the Committee found that mortgage companies on the continent are far less risk-averse than lenders in the UK, the latter who are relying on “discredited” scientific evidence.

The 'seven-metre rule' was proposed in 2012 by the Royal Institution of Chartered Surveyors (RICS) but has since been ditched because it lacks a robust evidence base.

Norman Lamb, the Committee chairman, said: "The UK's current approach is more cautious than it needs to be. We need an evidence-based and nuanced approach." 

The research suggests that damage to the one in 80 British homes Japanese knotweed affects is 'no greater than other disruptive plants', with it rarely travelling more than four metres. 

While the report acknowledges that Japanese knotweed can cause damage, it noted that recent evidence suggests the effects on buildings "might not be as significant as previously believed".

The Committee pointed to other invasive plants which do not have the same “chilling effect” on property prices.