The planned cuts to grant in aid have already had an impact, with Kew’s science directorate hit particularly hard. Kew estimated that in order to deal with a £5m annual deficit it needed to reduce overall staff numbers by 125 during 2014-15 – a sixth of the workforce. Headcount has already declined by more than 100 in the past year and further reductions are taking place.

Some 51 scientific roles at Kew were recently declared surplus to requirements and it has been estimated that up to 35% of the directorate’s staff could leave, especially if vacant posts are not filled internally.

Prospect negotiatior Julie Flanagan, said: “Today’s announcement by the government to reverse cuts worth £2.3m is welcome news, and follows a public outcry which has seen more than 100,000 people sign our petition. I now call on management to guarantee that there will now be no compulsory redundancies at Kew.

“However, the stark truth is that this announcement has already come too late to prevent long-term damage to Kew’s ability to carry out the vital scientific work for which it is world-renowned. The directorate has already lost more than 350 years of accumulated plant science experience. This is not easily built up or replaced.”

She added: “What Kew needs is a long-term sustainable funding plan, just as for other public bodies such as the BBC. Getting these short-term last-minute reprieves will not be sufficient to reverse the current loss of expertise and secure the long-term future and standing of plant science at Kew.”

The announcement of the government’s u-turn comes as MPs on the Science and Technology Committee prepare to take evidence on Kew’s funding at a hearing on Wednesday.

Prospect will outline how Kew’s current cuts programme in response to its funding situation is incompatible with carrying out its statutory obligations under the National Heritage Act, as well as the recommendations of the government-commissioned Chalmers Report of 2010. The union will say that nothing less than Kew’s global reputation as a leader in plant conservation and science is at stake.

Kew scientists are currently engaged in a variety of globally-important research projects including work on adapting agriculture to climate change in order to safeguard future food security. Through its Millennium Seed Bank at its Wakehurst site in West Sussex, Kew also aims to provide an insurance policy against the extinction of plants in the wild.