Home Secretary David Blunkett is expected to announce next week the decision to hire 1000 new members for the MI5 domestic secret service.
The extra staff, to be hired over several years, will mean a 50% increase in the size of MI5, taking it back to the manning levels it had during World War Two.
"It is understood that the recruitment drive … will include linguists, surveillance desk officers and staff involved in providing security advice to British business and industry," the domestic Press Association news agency said.
UK has been on an elevated alert, particularly since it joined hands with the US in its "war on terror."
The extra staff, to be hired over several years, will mean a 50% increase in the size of MI5.
MI5 is one of the pillars of UK intelligence, the others being the foreign spy agency MI6 and the electronic eavesdropping agency GCHQ.
The recruitment drive has expectedly been necessitated by heightened fears of "terrorist attacks" on UK.
"It is clear that terrorists are willing and able to attack British interests both at home and overseas," an unidentified intelligence source said.
Blunkett is expected to make a formal announcement about MI5 hiring next Wednesday.
On its website, mi5.gov.uk, MI5 says it already has vacancies for "generalists" and linguists fluent in Arabic, Persian, Punjabi, Russian, Turkish and Urdu.