The cost of replacing Trident has soared, the Conservative Government's defence review suggests.

The price of building four replacement Trident submarines has risen from £25bn to £31bn. 

But defence chiefs have also set aside an extra £10bn contingency fund, meaning the final bill could be as high as £41bn. 

Estimates that the overall life of the Trident successor programme will eventually cost between £100bn and £167bn have been based on the £25bn figure. 

The Strategic Defence and Security Review (SDSR) also raised the spectre of job cuts on the Clyde after minister's committed to build just eight new frigates there - not the expected 13. 

But it also includes new Maritime Patrol Aircraft which will be based at RAF Lossiemouth in Moray. 

Downing Street has suggested that MPs may be denied a vote on the final decision to replace Trident. 

A No 10 source said that the government was committing to a "debate" on the future of the nuclear deterrent on the Clyde. 

David Cameron has previously promised MPs a vote on the 'main gate' decision.

But the government's strategic defence and security review (SDSR) outlined plans to move away from a 'main gate' to a more gradual approach. 

A source said: "We are committing today to a debate". 

Later in the Commons David Cameron told MPs they would be given a vote on the replacement of Trident.