Some 100,000 ash trees have been felled in an effort to stop the spread of the deadly disease threatening to wipe out a species.
Environment Minister David Heath, MP for Somerton and Frome, said ash dieback could have "enormous potential consequences" as he confirmed a ban on imports of the species.
But shadow environment secretary Mary Creagh accused the Government of being "asleep on the job" for not taking action to protect ash trees at an earlier stage. The disease was first identified in ash trees in the UK in nurseries and recently planted sites, including a car park and a college campus, and last week officials confirmed it had been found in the wider countryside in East Anglia.
Updating MPs on the action taken so far, Mr Heath said: "On discovering Chalara in the UK, plant health authorities took immediate action to rapidly assess ash trees for signs of infection at over 1,000 sites where ash plants from Europe had been grown or planted in the last five years. This has resulted in the destruction of 100,000 trees."
But Ms Creagh said: "Ash dieback was found last February in a Buckinghamshire nursery. Why did ministers sit back, cross their fingers and wait until the disease was found in the wild in June?"
She claimed the Forestry Commission's budget had been cut by 25% and research funding had been reduced by £5 million in a year.