Plans to introduce mobile coverage on the London Underground have been held up in a dispute over how the necessary technology upgrades should be funded.

Transport for London (TfL) is understood to be pushing for mobile operators to hand over an ongoing share of revenues from phone calls and internet use on the Tube network. The funds would pay for the equipment and maintenance required to provide signals.

The mobile operators are meanwhile arguing that there would be no financial benefit from installing coverage underground.

The impasse is becoming increasingly urgent and political as the emergency services prepare to switch over to a new nationwide communications system based on EE’s 4G network.