The document will also acknowledge that the current fleet of four craft might be cut to three.

Both options would threaten thousands of jobs in Britain, as the UK has always relied on its nuclear arsenal being manufactured domestically.

The paper states: “It would be our intention to build the new SSBNs [ballistic missile submarines] in the UK . . . but this will depend on proposals from industry that provide the right capability at the right time and offer value for money.”

The remarks could anger Labour MPs, some of whom are already hostile to the idea that Britain needs a deterrent, and others who are relying on the 17-year programme of replacing the British fleet for jobs in their constituencies.

But Tony Blair may try to placate them and head off a Labour backbench revolt by announcing he is prepared to cut the number of warheads.

The government has decided to retain Britain’s independent nuclear deterrent by replacing its four Vanguard submarines, which are due to go out of service in the mid-2020s. The government needs to make the decision now because it will take nearly two decades to design and build their replacements.

The white paper will also say that the government wants to enter negotiations with the US about extending the life of the D5 missiles that the craft carry: they also reach the end of their life expectancy in the mid-2020s. The government was left little option because the missiles will become hard to maintain as the Americans move to new technology.

When Blair launches the white paper this week, he will argue that maintaining the independent nuclear deterrent is vital, given the emergence of new nuclear powers.

But the decision to publish the white paper on Monday, ahead of a special cabinet meeting on the issue, has caused dismay among some cabinet ministers, including Margaret Beckett, Peter Hain and Hilary Benn.

Yesterday, John Cruddas, one of the Labour MPs running for the deputy leadership of the party, said he was “not convinced” of the need to replace Trident.

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