London Underground maintenance workers have voted to strike in a dispute over pay and conditions.
The Rail Maritime and Transport (RMT) union said more than 90% of its members, employed by Tube Lines, have voted for strike action.
The unrest follows an announcement by Transport for London (TFL) that it will be buying out Tube Lines, which will still exist as a separate legal entity.
Bob Crow, general secretary at RMT: "We have sought concrete assurances staff will not be expected to pay off Tube Line's exit costs in job losses, attacks on safe working conditions and an undermining of pay rates. Now we have this massive mandate for action it is essential those assurances are forthcoming as a matter of urgency.
"With the transfer of Tube Lines, we expect TFL to take responsibility for maintaining the pay, jobs and conditions of the workforce it will need in place if it is going to get the upgrade programme back on track in time for the Olympics."
Read more articles on pay