Spies and civil servants who leak national security secrets face up to 14 years in jail, in a major overhaul of the Official Secrets Act in the face of the growing threat from Russia, the Daily Telegraph has learnt.

Foreign spies who steal information from the Government and leak it overseas, or those who snoop on British embassies, will also face prosecution in British courts for the first time, under plans to be considered by ministers.

Under the proposals, which are published today, officials who leak “sensitive information” about the British economy that damages national security could also be jailed.