Passengers face two weeks of disruption after London Underground staff announced six days of strikes over the fates of two sacked employees.
The Rail, Maritime and Transport union has said its Tube drivers would stage three walkouts lasting between nine and 24 hours each from 16 to 20 May and another three stoppages from 13 to 17 June.
Around 1,500 drivers will refuse to work. The strike was called after the two men dismissed last year were given "interim relief" by an employment tribunal pending full hearings.
The RMT claims such a move is granted only where there is clear evidence an employee was dismissed for their union activities.
London Underground says Arwyn Thomas was sacked over "abusive behaviour" and union activist Eamon Lynch because he "overrode his train's safety systems and drove with complete disregard for established procedures". The RMT said the dismissals, which led to a one-day walkout on the Northern and Bakerloo lines last year, had been proved unjust and the men should be reinstated.
Union leader Bob Crow said: "This is the clearest case of victimisation on the grounds of trade union activities that you will ever see.
"It's no wonder the employment tribunal was swift to see through the management lies. The solution is simple – LU should accept they have been found out and get these drivers back to work doing the job that they are being paid to do."
Transport secretary Philip Hammond condemned the strike as "absolutely no good" for the capital.
He added: "The unions need to understand that the future of industrial relations in this country is in their hands. There is no appetite in Government for a confrontation, but if the unions behave irresponsibly they are simply strengthening the arguments of those who want changes to our industrial relations laws."Reuse content