An extra £12bn will be diverted to the UK's defence budget under a five-year, cross-government security review to be unveiled by David Cameron today.
The Strategic Defence and Security Review, which is set to be outlined by the prime minister in a Commons statement this afternoon, has been led by the Cabinet Office, with contributions from the Ministry of Defence, the Department for International Development, the Home Office, and the intelligence and security services.
Several elements of the SDSR were trailed last week following the terror attacks in Paris – including a doubling of spending on cyber-security, extra resources for the three intelligence agencies MI5, MI6 and GCHQ, and a redirection of DfID's spending towards fragile states.
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Cameron is today expected to pledge a £12bn increase in the budget for defence equipment over the next decade, taking total defence spending to £178bn, while chancellor George Osborne confirmed over the weekend that Britain's counter-terrorism budget would rise by 30%.
Writing in The Telegraph, Cameron said: "Over the next decade we will invest more than £178 bn in buying and maintaining equipment – including doubling our investment in equipment to support our Special Forces.
"We will create two new strike brigades, forces of up to 5,000 personnel each, fully equipped to deploy rapidly and sustain themselves in the field. We will establish two additional Typhoon squadrons and an additional squadron of F35 Lightning combat aircraft to operate from our new aircraft carriers. And we will invest in nine maritime patrol aircraft to protect our nuclear deterrent, hunt down hostile submarines and enhance our maritime search and rescue.
"Not one of these capabilities is an optional extra or an act of vanity. These investments are an act of clear-eyed self-interest to ensure our prosperity and security."
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The SDSR comes a day after Osborne confirmed that all government departments have now settled with the Treasury ahead of Wednesday's government-wide Spending Review.
Speaking on the Andrew Marr show, Osborne downplayed reports of Cabinet splits with work and pensions secretary Iain Duncan Smith and home secretary Theresa May over the scale of cuts to their departments.
"I've read all these reports in the newspapers that I'm at war with various members of the Cabinet," Osborne said. "I can tell you, the Spending Review has been agreed, all departments have settled, and all settled amicably, nothing has been imposed and indeed this Spending Review has gone more smoothly than than the two previous Spending Reviews I've done."
However, the chancellor also refused to confirm whether or not he still intended to run a £10bn surplus by the end of the parliament, after figures released last week showed that public sector net borrowing was at its highest level since 2009.
Osborne said: "The precise level of the surplus will be set out in the OBR."