Britain will hire 1,900 more spies to combat ISIS in response to a spate of terror attacks including Friday's massacre in Paris.
The new hires will boost the total number of British intelligence staff by 15% to nearly 15,000, the biggest expansion since the 2005 terror attacks on London.
"In the wake of the increasing number of Islamist terror plots against Britain and the attacks in Belgium, France, Tunisia and elsewhere, the prime minister has decided to boost resources," the British government said in a statement.
Prime Minister David Cameron said Britain would also boost its spending on the military fight against terrorism by £2 billion ($3 billion) through 2020.
The announcement came three days after deadly terrorist attacks in Paris killed at least 129 people and injured 352.
The new security staff will be working across Britain's three intelligence agencies -- MI5, MI6 and the Government Communications Headquarters. MI5 is the domestic intelligence service, while MI6, formally known as the Secret Intelligence Service, operates abroad. GCHQ is the UK eavesdropping agency.
Britain spends about £2 billion ($3 billion) a year on the three services.
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The government is also doubling the amount it invests to protect Britain against cyberattacks. It will spend £1.9 billion ($2.9 billion) over five years and will establish the country's first dedicated cyber-force at GCHQ.
On top of extra resources for the military and intelligence services, the U.K. is also planning to more than double the amount it spends checking security at foreign airports.
The extra £9 million ($13.5 million) would provide additional aviation security experts to assess security at airports around the world, and the capacity to respond faster in the event of incidents such as the Russian Metrojet crash in Egypt two weeks ago.
The government said it was rethinking its approach to aviation security following that crash, which killed 224 people. The authorities now believe the plane was most likely brought down by a bomb.
Cameron said the U.K. will work with countries to put in place the "tightest security measures possible," prioritizing airports used by high numbers of Brits.
The assessments are likely to focus on passenger screening, physical security at airports, and hold baggage and freight screening.
"This is a generational struggle that demands we provide more manpower to combat those who would destroy us and our values," Cameron said.
The full details of the plan will be revealed in the government's five-year defense and security review next week.
