The disease hit the UK last year and was exclusively revealed in Horticulture Week in June.
Defra stated: "The Truth: Tree and plant health is an absolute priority in Defra and our response to tree diseases has been put on the same footing as our response to animal diseases. When chalara was identified in our trees and woodland the secretary of state Owen Paterson appointed a senior civil servant with extensive experience to ensure a swift and effective response. The team brought in people from across disciplines and organisations, including the Chief Plant Health Officer and other plant health experts from the Forestry Commission and Fera.
"The resulting action included conducting an urgent survey of ash trees across the whole of the UK that was unprecedented in our history, and organising a summit of experts with an interest in tree health to help develop the Chalara Control Plan.
"The scale of our response was reflected in the COBRA meetings chaired by the Secretary of State. It is also evident in the Plant Health Task Force convened by Defra’s Chief Scientific Adviser and chaired by Professor Chris Gilligan, which will make radical recommendations on how we should handle plant diseases.
"These are not characteristics of a chaotic response, but of a Government that acted quickly to get a grip of the unprecedented threat to our woodlands.
"Finally Pam Warhurst was not removed, as the Times suggests. Her term as Chair of the Forestry Commission came to an end and Owen Paterson has paid tribute to her robust and resolute leadership over the last three years."