Passengers will be able to use their mobile phones on stations on the London Underground (LU) by 2008.
Passengers will be able to use their phone at stations
London mayor Ken Livingstone has announced plans to install transmitters that will also allow access to wireless internet and digital radio.
But both the Lib Dems and the Conservatives warned the new technology could enable terrorists to carry out attacks from above ground.
A trial is set to be held next year at one station.
LU is now seeking proposals from suppliers to provide transmitters in stations and tunnels.
The company does not currently intend to provide coverage on Tube trains underground but, if feasible, mobile phone services could be extended across the network to include tunnels and moving trains at a later date.
Mr Livingstone said: "We know that many Londoners would like the convenience of being able to use their mobile phones at Tube stations throughout the Underground network.
"We also want to see how technology could be taken even further, for instance wireless internet so passengers could receive up-to-the-minute travel information via their laptop or mobile phone."
Concerns were raised by the Liberal Democrats last year about the security risks of such plans.
Former London mayoral candidate, Simon Hughes, said mobiles were a "cheap and effective long range detonator".
He added: "Using mobiles on the deep line sections... is unnecessary. Texting is a luxury, security is not."
Conservative transport spokesman Roger Evans said: "I think this is a good idea.
"My only concern may be that it could enable terrorists to set off bombs remotely and we need to consider that threat.
Responding to the security fears, an LU spokesman said there would not be a "greater risk".
"London Underground has robust procedures in place for dealing with unattended items on trains and stations," he said.
"We encourage our passengers to report any unattended item to a member of staff or the police immediately."