Described by environmentalists as one of the most momentous decisions of (British Premier) Tony Blair's leadership, the plant will cost hundreds of millions of pounds, despite being officially approved without parliamentary debate, sparking fury among MPs.

The plant will be able to test, design and build a new generation of nuclear bombs. Arms experts believe it will focus on smaller atomic warheads for use against terrorist groups and rogue states, reported The Observer.

Details to be submitted to West Berkshire planning authorities in the next 10 days reveal plans for one of the most state-of-the-art nuclear weapons plants in Europe.

According to the British daily newspaper, analysts warn that it appears to be a blatant breach of Britain's obligations under the nuclear non-proliferation treaty.

William Peden, nuclear disarmament expert at Green Peace, said: 'We are talking a massive nuclear bomb-making factory.'

The plans - confirmed by the Atomic Weapons Establishment - will involve closure of the 270-acre Burghfield site, where Britain's atomic warheads have been produced for almost 50 years. It will be replaced by a futuristic complex capable of designing atomic weapons as well as storing existing Trident warheads at AWE's 700-acre headquarters.

Details of the proposals were discovered in AWE's annual report, which refers to plans to 'transfer all operations' from Burghfield to the Aldermaston site.

The report also reveals proposals for a hydrodynamics research facility to help design and develop nuclear weapons, a £15 million supercomputer to simulate the effects of atomic devices and a factory producing tritium, a substance used to maximize the effects of a nuclear explosion.

An AWE spokesman said they had to 'maintain the capability to design a successor' to Trident, although the Government had not asked it to start work on one.

Paul Rogers, professor of peace studies at Bradford University, said: 'But at the very least, they want to build the infrastructure to create a new generation of weapons.

'It is clear that the Government is committing itself to a long-term nuclear future after Trident. This suggests a nuclear-free world more in theory than in practice.'

Menzies Campbell , Liberal Democrat Foreign Affairs spokesman, said that the British Government policy remained unclear.

'There has never been a serious parliamentary debate about a Trident replacement or what form it should take,' he added. 'But before embarking on expenditure of this size on an issue of such political controversy, at the very least Parliament ought to be consulted. I even suspect that the Cabinet may not have been involved in the decision. There are also legitimate concerns about facilities like this after September 11.'

The planning application will be submitted by the British Ministry of Defense on behalf of AWE, which is responsible for running Britain's nuclear weapons' sites.

The proposals must abide by normal planning procedures because crown immunity was removed after AWE - in effect, private contractors - took control of the running of Aldermaston in 1993. Planning officers do not have the power to reject the plans but, in the event of strong objection, can demand that Environment Minister Michael Meacher examines them.

Labour MP Martin Salter - who claims that his Reading West constituency lies downwind of Aldermaston - said: 'I am appalled that plans have been drawn up to extend the nuclear weapons plant at Aldermaston without reference to local communities, or indeed Parliament.'

On Monday, June 17, he will table a series of parliamentary questions about the Government's long-term nuclear policies, The Observer said.

The revelation arrives amid allegations that the UK is keen to pursue the Bush administration's lead in wanting to develop a range of tactical nuclear devices that can be used in a pre-emptive way against terrorist groups or rogue states.

America's recent Nuclear Posture Review Report details the need for an 'offensive' nuclear deterrent and a revitalized nuclear weapons complex with massive investment in facilities in order to modernize its weapons production capability.

Experts point to a series of statements from Defense Secretary Geoff Hoon in which he insists Britain has a right to use nuclear devices - pre-emptively if necessary - against states that are not nuclear powers.

Rebecca Johnson, executive editor of Disarmament Diplomacy, a leading independent journal in arms control, warned that U.S. and UK policy was becoming increasingly 'hand in glove'.

Ian Davis, director of the British American Security Information Council, an independent think-tank, said there was mounting evidence of increased co-operation between Britain and the U.S. on nuclear policy. Inquiries had found Labor becoming increasingly secretive over nuclear policy and demanded 'greater parliamentary scrutiny' over future decisions.

Investigations by The Observer confirm increased activity between U.S. and UK weapons officials. Parliamentary answers from Defense Ministers reveal the number of UK defense personnel visiting the U.S. grew substantially.