Plans will be unveiled today for new maritime patrol aircraft, extra fighter jet squadrons based in Scotland and more than 100 planes for the Clyde-built carriers to increase the UK's military 'punch’.

But the announcements come amid fears of base closures north of the Border and jobs cuts in Scottish shipbuilding.

In the wake of the Paris attacks 10 days ago the Prime Minister will today warn that the world is a more dangerous place than it was five years ago.

But he will also say that the key to national security is to ensure “our economy is, and remains, strong”.

Among the announcements expected as a result of the Government’s Strategic Defence and Security Review (SDSR) are an extra £12bn for equipment, two new “rapid” strike Brigades by 2025, and 138 new F-38 jets for the aircraft carriers.

But ministers are also expected to reveal base closures, cuts to the Navy and the Ministry of Defence and that some military units will be forced to disband or merge.

The Conservative Government is under intense pressure over national security in the wake of the horrific events in Paris.

The Chancellor George Osborne yesterday announced a 30 per cent increase in the counter terrorism budget, which he said would help make the UK safer.

Mr Cameron will also announce a £178 billion investment overall in defence equipment and support over the next decade.

The nine new Boeing P8 maritime patrol aircraft, which will carry torpedoes, will help protect Trident and the aircraft carriers as well as carry out surveillance and search and rescue operations.

Ministers have come under criticism for leaving the UK without maritime patrol aircraft the last SDSR in 2010, especially after a number of Russian shops have UK waters.

The UK Government will also extend the life the UK’s Typhoon jets, based at RAF Lossiemouth, for 10 years through to 2040.

This will also allow the RAF to create two additional squadrons, bringing the total number to seven.

The deal to buy 138 fighter jets will also treble the firepower of the aircraft carriers.

A total of 24 of the planes will be ready as early as 2023, up from the previous target of eight.

Mr Osborne said that British workers would benefits from the jets decision, which he said was worth £29bn to the UK supply chain.

The Prime Minister is also expected to make announcements plans to boost the UK’s ‘soft power’ and to focus aid on conflict regions and so-called ‘fragile’ states.

The defence review is also expected to include a greater focus on drones and as well as a commitment to push ahead with the planned renewal of Trident.

In his introduction to the SDSR Mr Cameron warns that the UK could not choose between “conventional defences against state-based threats and the need to counter threats that do not recognise national borders. Today we face both and we must respond to both.”

He said that the priorities over the next five years would be to “deter state-based threats, tackle terrorism, remain a world leader in cyber security and ensure we have the capability to respond rapidly to crises as they emerge.”

But there are concerns that Scotland could lose out with the maritime patrol aircraft based south of the Border at RAF Waddington in Lincolnshire.

The SNP have called any decision not to base the new aircraft in their “logical home” of Scotland a "betrayal and unacceptable".

They have also called for clarification from ministers on the future of the contract to build frigates on the Clyde.

Bill Kidd, the SNP MSP for Glasgow Anniesland, has written to the Defence Secretary Michael Fallon about reports that the contract for 13 new Type 26 frigates could be cut "to pay for Trident replacement".

Brendan O’Hara, the SNP’s defence spokesman, accused ministers of a “smoke and mirrors” exercise over defence.

He added: "David Cameron must address the concerns that the UK is now facing a defence capability gap - because of years of indiscriminate cuts - that is now potentially hampering our ability to respond to a new raft of threats .

“Decisions at Westminster have seen Scotland stripped of military assets and serving personnel handed redundancy notices, with more than 11,000 defence jobs lost in Scotland in the last decade.

“Yet while all of these deeply damaging cuts have been inflicted by Westminster, this Government remains committed to wasting up to £167 billion on replacing Trident even though new threats and dangers are emerging for which Trident will be completely useless.”