LONDON, June 9 -- Britain wants the power to imprison people for as long as 14 years for doing the bidding of a foreign state, even when they never go near a spy agency. A new bill introduced in the House of Commons on Tuesday would let the government treat the proxies of hostile states as if they were branches of a foreign intelligence service, the latest widening of a security apparatus that keeps enlarging the category of people it can prosecute.

The National Security (State Threats) Bill, brought forward by the government and reported on Tuesday, creates fresh criminal offences for bodies that a minister designates as acting for a hostile power. It borrows the machinery of the National Security Act 2023, so that a designated group ca...