Campaigners and politicians have hit out at the Conservative Government's push on Trident - before a vote by MPs.

Ahead of a visit to Scotland, Mr Fallon told The Herald that Trident renewal was "already under way".

He said that it was "extraordinary" for opposition politicians to "almost deny it is happening".

He has also announced another £640 million would be spent on updating the ageing weapons system – before MPs get a say.

And he said that the Commons vote would not be on the so-called 'maingate' decision on whether or not to replace Trident.

Instead, MPs will be asked to vote on the 'principle' of the nuclear deterrent.

The SNP have called for Mr Fallon to make a statement to the Commons on his comments.

57 of Scotland’s 59 MPs oppose renewal.

The SNP's defence spokesman Brendan O’Hara said that Mr Fallon's remarks were “shocking”.

He said: “A billion here, a billion there and another £640 million this week. It looks like the Tories are trying to renew this nuclear arsenal by stealth without bothering to consult the House of Commons.”

The Campaign for Nuclear Disarmament (CND) accused Mr Fallon of an affront to democracy.

“What is the point of a parliamentary vote on Trident if the government’s going to spend millions on replacement anyway?” said Kate Hudson, CND’s general secretary.

“This is completely unacceptable.”

Labour's shadow defence secretary Emily Thornberry also hit out at the lack of a maingate vote, saying: "It is yet more proof that - for the Tories - the debate on our future nuclear deterrent is not about national security, but just an excuse to play petty politics."