By Brenda Goh and Richa Naidu
April 29 (Reuters) - EnergySolutions said it was taking Britain's Nuclear Decommissioning Authority (NDA) to court after losing out on a $12 billion contract to decommission the country's oldest nuclear sites.
EnergySolutions, the incumbent manager of 10 nuclear sites, told Reuters it had filed the lawsuit in a British High Court.
The company had asked the NDA earlier this month to explain why it had awarded Texas-based Fluor and engineering company Babcock preferred bidder status for what is one of Britain's largest-ever government outsourcing contracts.
An NDA spokeswoman said the competition process had been carried out in "a robust manner" in compliance with European Union guidelines, adding that the contract was set to deliver savings in excess of 1 billion pounds ($1.68 billion) against EnergySolutions' previous plan.
EnergySolutions had teamed up with U.S. engineer Bechtel to make the bid that was rejected at the end of March.
A spokesman for Bechtel said the company had not joined EnergySolutions in its legal challenge.
A second consortium made up of Serco, Areva and CH2M Hill, and a third consisting of Amec , Atkins and Rolls-Royce, also lost out.
Sources told Reuters this month that at least two of the consortia had sent letters to the government requesting clarification on how it had picked the winning bidder, with the third reviewing its options. ($1 = 0.5950 British pounds) (Reporting by Richa Naidu in Bangalore and Brenda Goh in London; Editing by Dan Grebler and Ken Wills)