Leader of the RMT Bob Crow said the tube strike will go ahead after talks between London Underground bosses and the union failed to reach an agreement over pensions.
He said: "The action next week remains on and it is the management's intransigence that is responsible for the disruption travellers can expect."
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The decision represents something of a victory for the president who will now be able to enforce most of his controversial 90-day ban.
Cool in the north, warmer air to the south
Police have warned the drug, known locally as "pink champagne", could be deadly.