The announcement was buried in the explanatory notes to the five-paragraph bill to authorise Brexit, published on 26 January.

Prospect reacted strongly and issued a press release on 27 January. Deputy general secretary Sue Ferns said: “Although the government has presented exit from Euratom as a legal consequence of leaving the EU, experts contest this view. That is why we said the decision is ill-informed, irresponsible and unnecessary.”

The announcement has significant implications for the nuclear industry and the research that supports it, including:

• A requirement to conclude new bilateral co-operation agreements with the US and approximately 20 other countries to maintain access to intellectual property and nuclear technologies. It is likely that new treaties will take a long time to negotiate.
• Removing the requirement for the UK to comply with Euratom safety regimes, without which other countries will not be able to collaborate with the UK.
• Further potential delays and cost increases to the nuclear new build programme. The nuclear supply chain is international. Experts have warned that the movement of nuclear fuel, equipment and trained staff will become more complicated outside Euratom and the single market.
• Removing the basis for the UK hosting the Joint European Torus (JET) project. JET is the largest Tokamak in the world and is the only operational fusion experiment capable of working with tritium, the fuel necessary for fusion energy. More than 40 laboratories and more than 350 scientists and engineers from all over Europe currently contribute to the JET programme, which is funded by the European Commission.

There will also be broader, adverse impacts on employment, energy security and the economy.

Ferns said: “Many organisations and experts share our disquiet, but the timescale to challenge it is limited. The bill is being debated in the House of Commons on Tuesday 31 January and Wednesday 1 February. The committee stages of the bill are scheduled for 6 and 7 February.”

Prospect is urging members to:

• Contact their MPs urgently to register their opposition to this decision and tell MPs how it will affect them and their work. MPs’ contact details can be found on Parliament's website
• Share their correspondence with us so that we can use the information to lobby against the decision – including when the bill moves into the House of Lords. Please email [email protected]

“Prospect can use any information you provide on an anonymised basis. Please also send us a copy of any replies you receive from your MPs.

“If MPs receive a large number of emails on this topic, they will be forced to listen – and of course they listen most closely to their own constituents,” concluded Ferns.