Tube drivers and station staff have voted to strike over two separate disputes, the RMT union says.
Station staff voted to walk out over concerns for safety following the closure of ticket offices; while Piccadilly line drivers say there has been a "wholesale breakdown in industrial relations".
The news comes as another union, the Transport Salaried Staffs Association, announced it will ask its members to vote on taking strike action, saying they have been subjected to a rise in threats and abuse since the station closure programme started.
Mick Cash, RMT general secretary, said: "RMT members on the London Underground stations see day in and day out the toxic impact of the job cuts programme and they are reporting back that it is horrific.
"With the constant overcrowding on stations and platforms it is only a matter of time before there is a major tragedy if we don’t act decisively. Our dispute is about taking action to haul back the cuts machine and put safety back at the top of the agenda.
"In the separate dispute involving drivers on the Piccadilly line, safety is again a major factor and is tied in with the ripping up of policies and procedures and ignoring warnings from staff. Our members have been left exposed and vulnerable and we have no choice but to blow the whistle before lasting damage is done."
The results of the ballots will be considered by the union's executive before any action is taken.
London Underground said it does not tolerate any form of assault on its staff. It hasn't commented on the RMT strike vote.