The government has suffered a double defeat in the House of Lords on its plans to leave the Euratom amidst warnings that attempts to secure a replacement nuclear co-operation agreement (NCA) with the USA risk being delayed by Congressional deadlock.

The government lost votes on two amendments to the Nuclear Safeguards Bill, which is designed to create a new framework for the atomic industry co-operation, yesterday (20 March) afternoon.

The first amendment, which was carried by 265 votes to 194, suspends the UK’s withdrawal from the European Atomic Energy Community treaty until new safeguarding agreements are in place.

Lord Broers, the crossbench peer who moved the amendment, said: “This is essential if we are to maintain the nuclear baseload needed to underpin our intermittent renewables. If this fails, we will almost certainly not be able to meet our reduction in emissions obligation.”

Lord Hutton, chair of the Nuclear Industry Council, warned that international treaties had a track record of progressing “very slowly” through the Congress.

“Unless we are able to move seamlessly from the current NCAs to the new arrangements, the trade in goods and services will come to an end at the end of the implementation period at the end of 2020.

“If we get to that point where the NCAs are not in place with our key nuclear trading allies, we have a major problem. In my view, it would become impossible for the vital exchange of goods and services in the nuclear sector to continue beyond that point legally and lawfully, and if it cannot be done legally and lawfully then it will not be done at all.”

He was backed up by fellow Labour peer Lord Warner, who said the government’s “ill-considered and ideological rush to leave Euratom without being sure that an equivalent regime is properly in place” risked playing “Russian roulette with our energy security”.

He pointed to the reliance of the Sizewell B nuclear plant on a new NCA with the USA, which requires approval by the House of Congress.

Lord Warner said it was “far from certain” that a new NCA could be secured by the end of 2020, which is when the existing Euratom transitional period runs out, according to the EU-UK draft agreement published on Monday (19 March).

He said: “This is a legislature that is willing to shut down its own government in disputes over funding, so holding up an NCA with the UK is pretty small beer for the US Congress. It is far from certain that a new NCA with the US could be secured even by the end of 2020.

“It is likely to be a nail-biting experience, causing great uncertainty in the industry for the best part of two years.”

Lord Teverson, chair of the Lords EU environment and energy committee, said that failure by the UK to replicate Euratom’s existing agreements with the rest of the world and the International Atomic Energy Agency (IAEA) threatened to derail the UK’s nuclear new build programme.

He said: “There (is) a real risk of our current fleet of nuclear power stations coming to a halt, Hinkley C not being built and various other problems in terms of our deep work in nuclear research.”

Conservative peer Lord Trenchard acknowledged the UK could not guarantee how smoothly consent will be achieved in overseas legislatures for new NCAs but expressed confidence that it would be in other nuclear states’ interests to ensure nuclear safeguarding arrangements are maintained with the UK.

Opposing the amendment Business, Energy and Industrial Strategy (BEIS) minister Lord Henley said that postponing the UK’s withdrawal from Euratom arrangements would “unnecessarily create huge risks and uncertainties to the UK’s ability to operate as an independent nuclear state” following Brexit next March.

He also said the withdrawal conflicted with the transition period timetable agreed between the EU and the UK on Monday, according to which the UK’s Euratom arrangements will lapse at the end of 2020.

The government also suffered defeat on a separate amendment relating to nuclear research arrangements and trade in nuclear fissile materials post-Brexit.

The amendments, both of which will now have to be considered by the House of Commons, threaten to derail progress on the bill on which the government had hoped to secure Royal Assent by parliament’s Easter recess.