The government's "incompetence" helped spread the fungus that causes ash dieback disease, shadow environment secretary Mary Creagh has claimed.
Opening an opposition-day debate on the sperad of Chalara fraxinea on 12 November 2012, Ms Creagh said ash dieback, which has devastated Denmark's ash population, would "change our landscape forever".
"It is an environmental, ecological and economic disaster," she said.
Ministers were told in April that the disease had been discovered in a nursery, but a ban on ash imports was not introduced until October.
Ms Creagh told MPs: "Ministers could have started the consultation on a ban back in April instead of leaving it until the end of August. The question on everyone's lips is: 'Why didn't they?'"
Environment Minister David Heath dismissed Labour's criticism.
He said: "Perhaps it would be helpful to the House if I said that as of today the results of that survey show 155 cases of ash dieback caused by Chalara across Great Britain, 15 of these are in nursery stock, 55 are in recently planted sites and 85 are in the wider environment.
"Further suspect cases are currently under investigation and we'll continue to provide updates on confirmed cases through the Forestry Commission website."
Labour's motion "regretting" that the government did not take earlier action and urging ministers to assess whether the Forestry Commission has adequate resources to tackle the spread of the disease was defeated by 271 votes to 204, a government majority of 67.