Lawrence Livermore National Laboratory on Friday was declared the winner in a competition to design the nation’s first hydrogen bomb in two decades, a major step in restarting production of nuclear weapons.

The Bush administration said the programme, known as the reliable replacement warhead, will improve the US stockpile’s reliability, security and safety, as well as allow for a reduction in the thousands of weapons held in reserve for a potential future war.

But the decision triggered a sharp reaction from critics, who said it sends the wrong international message at a time the US is trying to stop the spread of nuclear weapons. Key members of Congress said the programme was moving too fast.

“I have serious concerns with the process leading up to today’s announcement, and with the priorities of the Department of Energy,” said Rep Pete Visclosky, chairman of the appropriations subcommittee that would pay for the programme.

“Although a lot of time and energy went in determining the winning design for a new nuclear warhead, there appears to have been little thought given to the question of why the United States needs to build new nuclear warheads at this time,” he said.

The award culminates a frenetic competition held since 2005 between Livermore in the San Francisco Bay Area and Los Alamos National Laboratory in New Mexico. Sandia National Laboratory, which provides engineering for the arming system, was part of both teams and its California branch will continue on the programme with Livermore.