Rail workers in the RMT union on South West Trains are set to be balloted for strikes over Olympic bonuses.
The firm had said there would be minimal change for workers during the Olympics.
Yet some 80,000 extra passengers are expected to travel through London Waterloo station daily.
The RMT has secured a £700 Olympic bonus for Heathrow Express staff and £400 for cleaners on the West Coast Main Line.
It is balloting staff who run the “Boris Bike” cycle hire scheme for strikes over Olympic bonuses and conditions.
Meanwhile tube workers in London Underground’s service control centres have voted by 80 percent for strikes to defend jobs and conditions.
And RMT members on the NorthLink ferry services to the Orkney and Shetland islands are to ballot for action against privatisation and to defend pensions.
RMT suspends strike after improved pay offer
The RMT has partially suspended strikes on the Tyne & Wear Metro after operating company DB Reggio made an improved pay offer. The firm originally offered 2.1 percent.
Metro workers struck on 7 June and were due to strike on Thursday of this week.
A separate dispute over pay and victimisation among Metro cleaners continues. Churchill, the contractor that employs the cleaners, is refusing the cleaners any pay rise.