The environment department has been accused of “panic” over Brexit after a leaked document revealed the emergency redeployment of staff to prepare for a no-deal scenario.

Managers at the Environment Agency (EA) were given just 24 hours to name 75 staff to be sent to the Department of Environment, Food and Rural Affairs (Defra). In September, the National Audit Office said Michael Gove’s department will not be ready for a no-deal Brexit, with meat and dairy and chemicals exports especially threatened.

The loss of staff at the EA has also raised concerns. It is responsible for protecting the country from flooding as well as water, land and air pollution, but lost a significant number of staff between 2010 and 2018.

The EA memo, headed “URGENT Action – immediate attention” and leaked to the Guardian, said: “We are gearing up our contingency planning for EU Exit and have been asked by Defra as a matter of urgency to provide staff.”

It was sent on 22 October, with staff asked to redeploy within a week. “We realise this is an extremely short deadline and that many staff will be on half term,” it said. “However, please do your best as part of our ambition to go the extra mile to help at this challenging time.”

Another 75 staff are being taken from other environmental agencies overseen by Defra, which include Natural England and the Animal and Plant Health Agency. The government will not reveal how many staff have already been seconded. Defra is responsible for almost a fifth of all the Brexit-related workstreams across government, covering the food and chemical industries, farming, fisheries and the environment.

Tim Farron, Liberal Democrat environment spokesman, said: “The news that Defra is desperately trying to get staff before Brexit day is deeply worrying, no matter the outcome of negotiations. This smacks of panic and desperation, as they try to dig themselves out of the hole they’ve dug. It means that deal or no deal, this government is deeply unprepared for the chaos Brexit will cause.”

Sue Hayman, Labour’s shadow environment secretary, said: “This panic in Defra comes just weeks after the National Audit Office (NAO) raised the alarm over the chronic lack of Brexit preparedness in Michael Gove’s department.”

“The Environment Agency has already been subject to brutal cuts by this government since 2010 and there are serious questions about the agency’s ability to respond to emergencies such as flash floods with this further hollowing out,” she said. “Michael Gove is rearranging deck chairs on a sinking ship.”

The number of core staff employed by Defra, rather than by its agencies, was hit heavily by budget cuts between 2010 and 2016, falling by 25% to 1,827. But since the vote to leave the European Union in June 2016, the number of staff has almost doubled.

Despite this, the NAO report concluded: “For some workstreams, Defra has passed the point where it will be able to deliver what it had initially planned for a ‘no-deal’ exit in March 2019.” The main roles urgently needed by Defra, according to the leaked memo, are in policy, project delivery and communication.

“Over 80% of Defra’s agenda is affected by Brexit and as a result, a number of staff from across the Defra group are now supporting our comprehensive programme of work,” said a spokeswoman for the Defra group. “However, we are clear this must not impact our commitment to protecting our environment and the vital work of the Environment Agency in areas such as flood protection or tackling waste crime.”

After the NAO’s report, Rebecca Hesketh, Brexit adviser at the National Farmers Union, said: “The NAO stated that the planning for many of Defra’s work streams was ‘poor quality’ and ‘lacked maturity’, with the department reportedly missing a ‘high proportion of its project milestones’. This lack of preparedness is worrying.”