The UK Government last night denied it had broken a promise not to make a final decision on the �Son of Trident� until after the next General Election.

The UK Government last night denied it had broken a promise not to make a final decision on the "Son of Trident" until after the next General Election.

It did so after it was revealed that one of its most senior officials had told a conference last year that Britain had already made up its mind to replace its Clyde-based nuclear deterrent.

The Ministry of Defence yesterday stood by its 2006 White Paper in which it said a decision on whether to buy a new generation of warheads, worth at least £3bn, would not be made until the next Westminster Parliament in the autumn.

But a document released to the Campaign for Nuclear Disarmament after a Freedom of Information request revealed comments by David Gould, the then-chief operating officer at the Defence Equipment and Support Organisation, stating the warheads would be replaced.

The documents quoted Mr Gould as saying: "The intention is to replace the entire Vanguard class submarine system. Including the warhead and missile."

Mr Gould was speaking to some 200 defence industry specialists at a special day event on the future of the deterrent in June 2007.

The Campaign for Nuclear Disarmament yesterday said the newly-revealed document suggested the House of Commons had been misled by the government.

Kate Hudson, the group's chairwoman, said: "This document destroys any remaining credibility in the government's claim that it has not yet made a decision on new nuclear warheads.

"Staffing at the Atomic Weapons Establishment has grown by one-third in the last five years, with billions spent on new facilities, yet throughout this the government has been telling MPs and the public that it would be years before any decision was needed. It is a disgrace that the MoD is secretly telling the defence industry one thing, whilst ministers are saying quite the opposite to parliament."

Angus Robertson MP, the SNP's leader at Westminster, said: "Scotland is united in opposing Trident nuclear missiles dumped on the Clyde, and it is totally unacceptable that the UK Government is secretly spending money on the Trident replacement while pretending that no decision has been taken. The Scottish Parliament and a majority of Scottish MPs have voted against Son of Trident', and the SNP will be demanding an explanation from the Defence Secretary for this undemocratic and furtive conduct."

An MoD spokesman yesterday played down the importance of the document, stressing it was a "speaking note" rather than a transcript of what Mr Gould said. The document was initially released with the crucial remark removed. The full version was only published after an appeal.

The MoD spokesman said: "Decisions on whether and how to refurbish or replace our existing nuclear warheads are likely to be necessary in the next parliament.

"To inform those decisions, we are undertaking a detailed review of the optimum life of the existing warhead stockpile and analysing the range of replacement options that might be available. No decisions have yet been taken. Decisions on a successor to the life exte nded D5 missile are not expected for some time and the new submarines are expected to remain in service beyond the current planned life of these missiles."

Jackie Baillie, the Labour MSP whose Dumbarton constituency includes Faslane, said: "It's entirely appropriate for officials to prepare for every eventuality but ultimately these things are decided by parliament."

Parliament has already voted to replace the ageing submarines, based at Faslane on the Gareloch, that currently carry Trident nuclear missiles. No decision, however, has been made on how - or even if - the nuclear warheads will be replaced as well.