The privet hedge, a symbol of  suburban Britain found in millions of private gardens, could be a  secret killer of the nation’s 80 million ash trees.

Other favourite garden plants – such as lilac trees and the flowering shrub forsythia – could also be harbouring the ash dieback disease, a Government scientific adviser warned last night.

Dr Woodward said: ‘Ash is a member of the olive family of trees and we need to find out if other species in the family are susceptible to the disease.

‘They may be carrying the fungus without being harmed, but when their leaves fall off they produce spores which could be affecting and spreading to ash trees.’