Broadcaster and physicist Brian Cox has condemned a decision by the Government to leave the European atomic energy regulator as "parochial idiocy".
Withdrawal from Euratom, the European Atomic Energy Community, was announced in notes accompanying the bill to trigger Article 50 on Thursday.
The organisation has been responsible for nuclear safety and security in Europe since 1957.
But Brexit legislation to leave the EU also means withdrawal from Euratom, a separate legal entity governed by EU institutions, because under the European Union Act 2008 the term "EU" includes Euratom.
The decision is expected to have major implications for Britain's nuclear industry and necessitate new international agreements over access to technology.
And it has been met with derision by some in the science community.
Prof Cox said: "I'm trying to use temperate language, so here goes: Terrifically stupid, utterly shitheaded, myopically parochial idiocy. Pointless damage."
Steven Cowley, former chief executive of the UK Atomic Energy Authority, said leaving Euratom would be a "tremendous blow" to UK nuclear research and Iter, an international nuclear fusion project being built in France.
The future of the Culham Centre for Fusion Energy, the UK's national laboratory for fusion research, also faces a blow from the decision as around two thirds of its budget comes from Euratom.
Prof Cowley told the research policy publication Research Fortnight: "It is critical that the UK stays heavily involved in Euratom.
"By pulling out from Iter, the UK will be damaging both the programme and our own domestic research. Britain contributes some of the European cost of Iter but, more importantly, the UK leads on science and engineering.
"Iter will probably face delays and struggle with technical issues without the British on board."
A spokeswoman for the Department for Exiting the European Union said: "Leaving Euratom is a result of the decision to leave the EU as they are uniquely legally joined.
"The UK supports Euratom and will want to see continuity of co-operation and standards. We remain absolutely committed to the highest standards of nuclear safety, safeguards and support for the industry.
"Our aim is clear we want to maintain our mutually successful civil nuclear co-operation with the EU."