THE white collar rail union TSSA has joined the RMT in staging 48-hour Underground strikes next month, after its members voted in favour of the walkouts by a majority of 58.8 per cent.

TSSA general secretary Manuel Cortes claimed that Transport for London's plans to close all Underground ticket offices and abolish permanent station supervisors would be a safety gamble, and he called on the Mayor of London Boris Johnson to restart talks.

He said: "It is now time for Boris to sit down with his staff representatives and negotiate a sensible deal which will protect the safety and security of the travelling public as well as the long term interests of our members."

The strikes are set to take place from midday on 4 February until midday on 6 February, and again from 11 to 13 February.

Transport for London has announced that more than 1,000 volunteer 'Ambassadors' will be deployed to keep stations open where possible during the strikes, and promised that in spite of the ticket office closures there would still be a job for any member of Underground staff who is willing to be 'flexible'.

Meanwhile, a separate RMT strike on the Docklands Light Railway has been called off. It was due to take place on 29 and 30 January.