Union leaders said the workers are amongst the most exploited in London
About 700 cleaners working on the London Underground will stage a series of strikes to demand more pay.
The cleaners, members of the Rail and Maritime Transport (RMT) union, will go on a 24-hour strike on Thursday and then a walk-out for 48 hours on 1 July.
The workers are demanding that four private Tube contractors give them a London "living wage" of £7.20 an hour instead of the current £5.50.
Transport for London (TfL) said the strikes were "completely unnecessary".
'Exploited and abused'
A TfL spokesman said: "Following the transfer of Metronet to Transport for London, we will be working with Metronet and its sub-contractors to ensure that they pay their employees who work on the Tube the London Living Wage."
But RMT leader Bob Crow described the current pay and conditions as "outrageous" and said cleaners were not entitled to receive sick pay, travel facilities or a decent pension.
He said there was overwhelming support for industrial action, with union members voting 125-1 in favour of a walk-out.
"This was a massive vote for action by a group of workers who are among the most exploited and abused in London," he said.
The RMT also called for an end to the practice of cleaners being fired from their jobs without a disciplinary hearing or right to appeal the decision.