Oyster cards on all rail lines in a year, vows Boris

The Mayor said he wanted to "fully integrate" overground and Underground services so that the cards could be used by those travelling from stations in outer boroughs.

He also said this would have benefits for those who have cut-price travel with Oyster cards but not on mainline rail tickets.

The proposals came as he endured a grilling during the first People's Question Time event of his mayoralty.

The Mayor, who has now been in office six months, fielded questions before 600 Bromley residents on issues ranging from policing to airport expansion.

He was caught out by 17-year-old Christopher Price who informed him that travel for 16- to 18-year-olds was not free on Tubes and trains as the Mayor had believed.

Mr Johnson said: "There should be much greater integration between overground and Underground and it's one of the things we're going to do by the end of next year.

"For instance we are going to have the consistent, fully Oysterised system. I want people to be able to use their Oyster card at any station within the greater London area whether on the overground or the Underground and we're going to get that agreement from the train operating companies and once you've done that the beauty of it is you can start integrating both sorts of rail.

"At last you can have a serious, sensible map that states all the links between the overground and Underground. I would like to build on the success that TfL has had in running the North London Line."

The Mayor also sought to reassure residents that they would see real benefits from the 2012 Olympics, despite the borough not hosting any events. He reaffirmed his pledge that the cost to Londoners would not by more than £20 a year.

But Mr Johnson did not want to answer any questions on the next Met Commissioner saying he would "dodge, dip, dive and duck" any such queries.

People's Question Time events have traditionally been held twice a year since the London Assembly was formed in 2000. But Mr Johnson has promised to increase the number to six a year with meetings being held in every GLA constituency during his first term.

Speaking at Bromley Civic Centre, Mr Johnson said: "I want to hear directly from Londoners about the issues that matter to them and affect their everyday lives."

Outside the hall trouble broke out as up to 100 people, some of whom had tickets, tried to gain entry but were told to leave by police as the event was full.