(Updates with Lords committee report)
By Nina Chestney
LONDON, May 2 (Reuters) - Britain's plan to leave the European Atomic Energy Community (Euratom) when it quits the European Union will severely hinder nuclear trade and research, and threaten power supplies, a UK parliamentary committee said in a report on Tuesday.
The government says Britain must leave Euratom as part of its goal to end the jurisdiction of the European Court of Justice when the country leaves the EU.
Experts have said that if Britain leaves Euratom, there is a risk of new-build projects being delayed or put on hold while new stand-alone nuclear cooperation treaties are negotiated with countries in the EU and outside it.
Euratom is the EU's framework for nuclear energy safety and development, establishing a European market for goods and services and compliance with international safeguards to control the use of uranium and plutonium.
Although it is legally separate from the EU, it has the same members and is governed by EU institutions.
In a report, the cross-party Business, Energy and Industrial Strategy Committee said the gap between Britain leaving Euratom and setting up alternative arrangements would hamper nuclear trade, research and nuclear energy supplies.
"The impact of Brexit on Euratom has not been thought through. The government has failed to consider the potentially severe ramifications of its Brexit objectives for the nuclear industry," said Iain Wright, chair of the committee and a lawmaker from the main opposition Labour party.
The committee said the government should delay Britain's exit from Euratom until new arrangements are set up.
Britain needs to invest in new infrastructure to replace aging coal and nuclear plants set to close in the 2020s, but has struggled to get large projects, especially nuclear, built.
EDF's 18 billion pound ($23 billion) Hinkley Point C nuclear project in southwest England got the final go-ahead in 2016 after several years of delay, but only after securing backing from the French government.
A separate report, published by the cross-party House of Lords Science and Technology Committee, called on the government to set its strategy for Britain's nuclear future if more new projects, including small modular nuclear reactors (SMR), are to be built.
"If the government's aim is for the UK to be active across the main areas of nuclear R&D it needs to make significant investments in new technologies or we risk falling behind the rest of the world," committee chairman John Palmer said.
Early last year Britain committed 250 million pounds to nuclear research, including a competition to identify the best-value SMR design for the country. However it has yet to publish the results, frustrating project developers.
SMRs use existing or new nuclear technology scaled down to a fraction of the size of larger plants.
$1 = 0.7748 pounds Additional reporting by Susanna Twidale; editing by Susan Thomas