During his radio phone-in on LBC 97.3, Boris Johnson told Bob Crow: "What you have got to do is call off this pointless strike which will do nothing but cost your members. London's Mayor told the RMT Union leader to "do the right thing for yourself, for your members for London, get round the table."
Pictures from LBC 97.3
The confrontation came during the Mayor's monthly phone-in show on LBC 97.3 - thought to be only the second time the two men have spoken.
The dispute over ticket office closures was deadlocked tonight with millions of commuters almost certain to be caught in the crossfire.
London Underground says services will be affected from around 9:30pm on Tuesday 4 February.