Northern Rail operates services throughout the north of England
Thousands of rail workers across the north of England are to be balloted for strike action over a "comprehensive breakdown" in industrial relations.
The Rail Maritime and Transport union (RMT) claims relations with management at Northern Rail have plummeted to an all-time low.
The firm operates in the North East, Cumbria, Lancashire and Yorkshire.
A company spokesman said it planned to meet union officials and hoped to reach a resolution to the problems.
The union claimed its reps had been victimised, new working conditions imposed, disciplinary procedures breached and changes made to payments to staff assaulted on duty.
General secretary Bob Crow said: "Industrial relations at Northern have plummeted to a new low, and our members are telling us that the company's aggression must be challenged.
"In the last three months the company has fired two union reps for alleged breaches of conditions that have been imposed without agreement, and cynically manipulated its own disciplinary procedures in the process.
"We have also seen the company fail to produce written assurances we were promised that guards would be in place during trials of new tram-trains on the Penistone-Huddersfield line, and now there are also moves to undermine promotion prospects for our members."
A Northern Rail spokesman said a meeting was planned with union officials for Friday.
He added: "We are looking forward to a positive meeting and are very hopeful that those issues can be resolved."