The proposed enhancement of British security includes a promise of a 15 per cent increase in staff for the spy agencies, MI5, MI6 and GCHQ, to respond to tackle terrorism and cyber attacks.
The prime minister will set out the plans as the government finalises its five-year strategic defence review, which will be published next week ahead of chancellor George Osborne's public Spending Review.
Mr Cameron and Mr Osborne will frame the two packages as being about enhancing Britain's "security", whether from the threat of global terrorism or against the risk of a future economic crash.
The chancellor will argue that by cutting spending elsewhere, notably on welfare, he has found the cash needed to boost Britain's defences, whether in intelligence, the military or counter-terrorist policing.
Mr Cameron, who will make a speech on global security in the City of London tonight, will say: "I am determined to prioritise the resources we need to combat the terrorist threat.
"This is a generational struggle that demands we provide more manpower to combat those who would destroy us and values."
The G20 summit at the Turkish Mediterranean resort of Antalya has been dominated by the Paris attacks and world leaders discussed the terrorist threat last night at a working dinner.
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British security services have embarked on a big operation over the past two days in response to what security analysts have said is a significant shift in the tactics of the Islamic State of Iraq and the Levant (Isis).
Screening checks at ports had been increased and there will be extra police at the borders and on the streets, Theresa May, home secretary, told the BBC's Andrew Marr programme. The security services had been preparing for an urban attack similar to the events in Paris since the terror attacks in Mumbai in 2008, she said.