Police radios will now work in all 125 below-ground London Underground (LU) stations after the Airwave police radio network was extended to provide coverage.

Airwave is a secure radio service used by the police and ambulance services in England, Scotland and Wales.

In 2007 a report by a London Assembly committee reviewing the 7 July Tube bombings highlighted lack of police radio contact underground as a serious concern.

Coverage on the Tube was not included in the original Metropolitan Police contract signed in 2001. Following a £55m deal in December 2006, Airwave has linked the police network with the Connect system used by LU train drivers, according to Tim O'Toole, managing director of LU.

"LU and the Home Office together with partners had the foresight to fund works to facilitate the link-up between Airwave and our new radio system prior to the Airwave contract being signed because of the benefits we knew it would deliver," he said.

Police minister Vernon Coaker will visit Westminster tube station today to see the system in action.

"Crime is down on the Underground and with the rollout of Airwave, passengers can feel even more confident that every effort is being made to keep them safe as they travel around the capital," said the minister.

But there are some concerns among police over the radios' effectiveness in dense, built-up areas.