A government horticulturalist has criticised BBC gardening shows for encouraging viewers to plant foreign species that risk spreading disease.

Defra's chief plant health officer Prof Nicola Spence branded TV show Gardeners' World “irresponsible” after a feature on growing olive trees.

She said star presenters like Monty Don should not be encouraging gardeners to grow olives because they are a high risk for importing deadly plant disease Xylella fastidiosa.

Speaking at a biosecurity event at Tendercare Nurseries in Uxbridge, west London, last week Prof Spence said: "Gardening trends can drive biosecurity behaviour.

"I like to watch Gardeners' World on a Friday night and to listen to Gardeners' Question Time, but I occasionally have a bit of a rage at them and take to Twitter when I think they're not providing the best advice, particularly when a listener - somebody in the audience - says 'I've just brought back X from my holidays. What should I do with it?'