The British government has sold its final stake in the country's nuclear weapons plant, prompting criticism from lawmakers who said Saturday it throws the independence of the British nuclear deterrent into question.

State-owned British Nuclear Fuels Limited (BNFL) sold its one-third stake of the Aldermaston Atomic Weapons Establishment (AWE) at Aldermaston, Berkshire, west of London, to Jacobs Engineering Group of the United States.

The remaining two-thirds are already owned by US defence giant Lockheed Martin and Serco of Britain.

Aldermaston is where Britain's Trident nuclear warhead, which is launched from submarines, is designed and manufactured. It has been the focus of anti-nuclear protests for decades.

The move was announced in a brief statement on the BNFL website which said: "BNFL is delighted to confirm that it has today agreed the sale of its one third shareholding in AWE Management Limited to the Jacobs Engineering Group."

The stake was put up for sale last year after ministers decided to break up BNFL.

The main opposition Conservatives called for a government explanation, saying the AWE was "critical" to Britain's nuclear deterrent capability.

Nick Harvey, defence spokesman for the Liberal Democrats, told the BBC: "The whole argument used for Britain having a separate weapons establishment is that this is required by the non-proliferation treaty, as technology sharing is not allowed.

"We must therefore query the rationale of a US company having a majority shareholding in AWE. How does this all square?"

The Ministry of Defence said in a statement: "UK sovereign interests remain protected at all times, as does the independence of the UK deterrent. The safe operation of AWE will remain unaffected by the sale."