A strike by drivers on a busy London Underground line will go ahead on Monday after peace talks broke down.
Members of the Rail, Maritime and Transport union on the Northern Line will walk out over the sacking of a colleague.
RMT general secretary Mick Cash said: "Talks at Acas, which RMT had been calling for with the objective of reaching a fair and just settlement in this case, have broken down due to a total refusal of the management side to engage in any kind of meaningful discussions.
"As a result of London Underground's disregard for negotiations and their own procedures Monday's action goes ahead as planned."
Phil Hufton, London Underground's chief operating officer, said: "The RMT has absolutely no basis to take strike action after one of their members was dismissed for failing an alcohol breath test.
"To ensure the safety of our employees and customers we operate a zero-tolerance policy towards alcohol at work. At no point to date has the RMT leadership disputed our alcohol testing process, which is fully in line with medical standards and is representative of best practice in the rail industry."
LU said it will try to run a good service on the Northern Line during the strike but warned there may be some disruption.