Tube services could be hit after RMT transport union staff on the Underground voted in favour of industrial action over a series of disputes.
RMT train staff on the Piccadilly line have voted for a strike in a row over agreements and procedures.
Also, drivers at a range of depots serving the Hammersmith & City, Metropolitan and Circle lines have voted for industrial action short of a strike in a dispute arising from the introduction of new trains.
The RMT also announced that Tube cleaners working for Danish multi-national ISS on London Underground have voted by 100% for strike action in a dispute over pay and conditions.
In addition, electricians and engineers working for contractors Mitie on a Transport for London contract have voted for strike action in a dispute over redundancies and working conditions.
RMT general secretary Bob Crow said: "The outcome of these separate ballots will now be considered by RMT's executive but the message could not be clearer - we are stepping up the fight to protect agreements, jobs and working conditions across the whole of London and to eliminate the scourge of poverty pay on cleaning contracts."
London Underground's operational development and upgrades director, Nigel Holness, said he was disappointed at the threat of industrial action over new trains.
He said good progress had been made in talks with the RMT on Wednesday and a further meeting was planned today.
"I would urge the RMT to work with us to bring about these improvements and remove the completely unnecessary threat of pointless disruption from hanging over our customers," Mr Holness said.
On the Piccadilly line ballot, Phil O'Hare, LU's Piccadilly line manager, said he was hopeful the issues with the RMT could be resolved.
He said there had been two "very positive meetings" with the union, and management was "due to meet with the union's regional organiser next week to finalise an agreement".