Chancellor Gordon Brown last night threw his weight behind replacing Britain's ageing nuclear deterrent.
In a speech in the City of London Mr Brown called for the a more advanced system which is expected to cost billions of pounds.
The Chancellor gave his personal backing to replacing the system ahead of a Government decision.
The Government has said that a decision will have to be taken in this Parliament on whether to replace Trident with a new nuclear deterrent.
Mr Brown's remarks are being interpreted as a move by him to align himself firmly as Tony Blair's successor by reassuring Blairites that he is firmly in the New Labour Camp.
Shadow Defence Secretary Dr Liam Fox described the expected comments in the annual Mansion House speech as "spin".
"This is just more spin designed to cast Gordon Brown as a statesman," he said.
"His words are exactly the same as those in the 2005 manifesto and are not new.
"The Chancellor is reheating an old pledge to retain the current nuclear deterrent, but he is not committing to replacing the independent nuclear deterrent when it reaches the end of its current life.
"Yet again Gordon Brown is playing fast and loose with the truth."
Shadow Chancellor George Osborne said: "We welcome Gordon Brown's commitment to maintaining independent nuclear deterrent - though quite why he is making such a song and dance about repeating the exact words that were in the Labour Party Manifesto just a year ago is a mystery."
European Commissioner Peter Mandelson told Channel 4 News: "I'm sure he has considered his position very carefully and I'm sure the speech will spark a very interesting n ational debate on the subject."
Liberal Democrat defence spokesman Nick Harvey said: "Gordon Brown's posturing on Trident is smothering the national debate that this Government promised to the British people.
"Regular Liberal Democrat Parliamentary Questions have brought repeated denials from ministers that work on options for Trident replacement has even started.
"The British people deserve a comprehensive White Paper and full parliamentary scrutiny of a scheme that may cost up to £25 billion to replace," he added.
Kate Hudson, chair of the Campaign for Nuclear Disarmament (CND), accused Mr Brown of pre-empting a public debate on the question and said that such a move would be hypocritical given the current concern over Iran's nuclear position.
"We are appalled at Mr Brown's support of a new generation of nuclear weapons to replace Trident," she said.
"For the person who will likely be Prime Minister in the near future, his stance may be pre-empting the full public and parliamentary debate which Tony Blair has promised.
"There has also been overwhelming support from the public for a deciding vote in Parliament on Trident replacement.
"We fully support those MPs who demand that the deciding vote should be taken in Parliament.
"This issue is too serious to be taken behind closed doors. The people's elected representatives must decide."
She added: "A decision to replace Trident would be nuclear hypocrisy.
"To actively pursue a new nuclear arms race in that way will only contribute to global tensions and lead other countries to conclude that they also need to develop nuclear weapons."