Two different groups of London Underground workers are to be balloted for strikes in separate disputes over jobs, pay and conditions.
The Rail, Maritime and Transport union (RMT) said scores of control centre and maintenance staff will be urged to back industrial action.
Some of the workers are employed by a contractor, which the union said had rejected a claim for an Olympic bonus payment.
RMT general secretary Bob Crow said: "Both of these disputes are about protecting our members' jobs, working conditions and standards of living in the face of aggressive and bullying management tactics that leave us no choice but to ballot for action.
"RMT remains available for talks but no-one should under-estimate the level of anger amongst both of these groups of workers."
:: Tube services were disrupted again today because of problems on the Bakerloo line.
It was the latest in a string of signal failures and train breakdowns which have caused travel misery over the past week.
Nigel Holness, network services director for LU, said: "As part of the Tube upgrade plan, we are installing new signalling on the Metropolitan, District, Hammersmith & City and Circle lines - which will improve services for our customers by greatly increasing capacity.
"This modernisation will result in the use of a single new service control centre at Hammersmith from 2017, rather than having a number of outdated signal cabins, some of which date back to 1926, and various service control centres spread across different locations.
"We are working with our staff to help them prepare now for changes that will be implemented in five years' time - finding out if they wish to stay in service control or choose a different path within LU.
"We have been in discussion with the unions across the entire Tube network, including the sub-surface lines, since 2007 on the impact of changes arising from our upgrading of signalling systems.
"On other lines - including the Jubilee, Victoria and Northern lines - we have successfully managed the movement of staff to new service control centres, and intend to follow a similar approach in this case.
"We are disappointed that the RMT have decided to ballot when discussions are ongoing and up to this point constructive."