City Hall confirmed that providing phone reception to Londoners on the tube was one of the mayor's ambitions to improve connectivity across the capital.
There is estimated to be well more than 100 miles of tunnels on the tube network , which makes them London's largest black spot with no mobile reception or Wi-Fi available to passengers.
Over the last five years there has been Wi-Fi available on platforms and stations, with the new project seeing the Mayor's office team up with an external provider to allow tube passengers to stay connected for the duration of a journey.
Crossrail , which will cuts through much of west London in underground tunnels, promises to have WiFi on board the trains.
Other global cities such as Hong Kong and Tokyo have fully connected 4G networks on their transit systems, while Chicago has had some connectivity on underground sections of its "elevated metro" since 2005.
"We are looking at how to improve connectivity across London, including on the Underground network" said a City Hall spokesman.
"The mayor is keen to do more in terms of keeping Londoners connected even when they're underground."
There is no timescale yet for when we may be able to answer calls, emails and even tweet on the tube as we would above ground.
A Transport for London spokesman said: “We are keen to offer full mobile phone coverage for our customers.
"The introduction of this would need to be commercially viable and would follow engagement with staff and customers.”
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