Tube drivers on part of London Underground (LU) have started a strike over the dismissal of a colleague.

Rail, Maritime and Transport (RMT) union members on the Northern Line walked out at 04:30 GMT for 24 hours.

Phil Hufton, from LU, said the RMT “has absolutely no basis” to strike and their member was dismissed for “failing an alcohol breath test”.

But RMT general secretary Mick Cash dismissed the claim that alcohol was involved as “totally untrue”.

He said the driver had a “specific medical condition” and LU had failed to follow procedures which had “led to this unwarranted dismissal and the subsequent strike action”.

The conciliation service Acas held talks on Friday in an attempt to avert the strike action but these broke down.

LU said it hoped to run a good service on the Northern Line during the strike but warned there may be some disruption.