Train services in Watford, Bushey, and Kings Langley could be hit by industrial actions after a rail union attacked proposed redundancies at London Midland.
The RMT union has criticised the rail company’s plans to axe 150 jobs saying the scheme will "decimate" frontline staffing.
The union is threatening an "all-out-fight" with London Midland over the planned job losses - which could involve strike action.
London Midland announced last Thursday that it was initiating the redundancy programme due to rising costs.
In a statement the RMT attacked the way the announcement was handled saying its members were not formally told about the plans until Friday.
Mick Cash, the unions acting general secretary, said: "It is disgraceful that this cuts bombshell was dropped on staff by London Midland through the media - staff have been sent threatening letters telling them that their jobs and livelihoods are on the block without any explanation as to why.
"The cynical attempt to claim that the 150 jobs threatened are not important is a kick in the teeth for staff who make London Midland tick - the plans have generated a wave of anger across all grades.
"RMT will now look at an all-out campaign, up to and including the use of industrial action, to stop these cuts, lift the gun from our members’ heads and get proper and meaningful negotiations back on track."
The union also described London Midland’s statement that the cuts would not affect frontline services as a "cynical attempt to mislead the public".
In a statement issued last week Patrick Verwer, managing director of London Midland, said: "The service to our passengers will not be affected by the changes. We have made good progress over the last year. Our train service is much improved and higher customer satisfaction scores tell us passengers can see the difference.
"Like every other business however, we have to keep our costs under control. Our proposal has been designed to increase efficiency and reduce our costs while continuing to improve trains and station services."