Drivers on London Underground are to stage a series of strikes in a long-running row over the sacking of a colleague, threatening travel chaos for millions of Tube passengers.
The Rail Maritime and Transport union said its members will walk out for between six and 24 hours on four occasions between June 19 and July 1, hitting commuters, overseas visitors to the capital and other travellers.
The strikes are over a continuing dispute involving the sacking of Northern Line driver Arwyn Thomas, whose claim of unfair dismissal has been heard by an employment tribunal, with the result expected in the coming weeks.
London Underground said it is "mystifying" that strikes are being threatened before the tribunal's decision.
Drivers will strike between 9.01pm on June 19 and 3am on June 20; between 9.01pm on June 27 and 11.59am on June 28; between noon on June 29 and 11.59am on June 30; and between noon and 9pm on July 1.
The RMT claimed that Mr Thomas, a long-standing union activist and driver based at Morden, was sacked on "trumped-up" disciplinary charges following allegations made against him during a previous strike.
Another driver, Eamonn Lynch, was also sacked, over a safety-related incident, but has been reinstated to a non-driving job after winning his claim of unfair dismissal at an employment tribunal.
The union's general secretary Bob Crow said: "RMT has made every possible effort to get Arwyn Thomas back to work and it is the intransigence of LU management, who have dragged their heels and failed to reach agreement over the past month, that has left us with no choice to put this strike action on."
A Transport for London spokesman said: "We committed in good faith to legal discussions ahead of Mr Thomas' tribunal. Unfortunately, no agreement was reached. We have always made clear to the RMT that we would respond appropriately to the tribunal's finding.
"We remain determined to improve the industrial relations climate and have been working with the RMT to ensure a jointly sponsored independent overview of disputes takes place. This recent positive engagement makes it all the more incredible for the RMT leadership to threaten Londoners with strike action once again, particularly as it was backed by just 29% of its members."