In March Transport for London announced Virgin Media would provide paid-for WiFi access as part of a deal which would see the cable company provide a travel information portal for passengers.
The WiFi will be available free only until the end of the Paralympic Games, after which commuters will have to pay Virgin Media for access.
London Underground has previously suggested other networks and providers may sign deals with Virgin to secure access for their users.
In a written answer to London Assembly Member Caroline Pidgeon, Johnson revealed that “14 companies expressed an interest” in bidding but of the seven companies invited to tender, four subsequently “declined” to do so.
Johnson said the “concession was awarded on the criteria of the most economically advantageous tender.”
The Mayor said “it is envisaged that wi-fi will be accessible from station entrances to platform level.” The service will not be available on Tube trains or in tunnels.
However Johnson was unable to provide Pidgeon with a list of the 120 stations where the service is expected to be rolled-out.
Officials have so far failed to answer a number of questions tabled by Pidgeon including those related to TfL’s expected income under the deal and whether any “alternative bidders [offered] full and free access Wi-Fi for all passengers”.