London Underground drivers are to go on strike on Boxing Day in a row over Bank Holiday pay.
Members of Aslef will are to hold three 24-hour walk-outs - on December 26, and again on January 18 and 25.
It is feared the move - which Aslef members backed by a 9-1 margin - will spark travel chaos in the capital
An Aslef spokesman said: "The ballot result shows the strength of feeling that remains on this issue.
"The union is committed to finding a solution which offers voluntary working and compensates those who do attend."
It will be the third successive Boxing Day walkout by Tube drivers in a dispute over Bank Holiday pay which dates back to an agreement in 1992.
The stoppage will disrupt Tube services on a busy day in the capital, causing big problems for shoppers, sports fans and visitors.
Talks have been held at the conciliation service Acas but the dispute remains deadlocked.
Howard Collins, London Underground's chief operating officer, said before the strike dates were announced: "We have been in discussions with the Aslef leadership to find a way to end this dispute and we made what we believed was a very fair offer.
"Unfortunately, this was not accepted and the offer has now been withdrawn so that further options to resolve the issue can be explored with the union at Acas.
"Further industrial action will not achieve anything and I would urge Aslef leadership to work with us to resolve this dispute."