Passengers could see their train journeys disrupted by strike action in a row over pay.
Rail operator Northern is facing industrial action from the Transport Salaried Staffs’ Association union in a long running dispute.
The union general secretary, Manuel Cortes has written to Northern chief executive David Brown to warn that if ‘copper bottomed guarantees’ on wages are not forthcoming by Friday they will consider further action.
The station, clerical and engineering staff are seeking a pay rise in line with the RPI measure of inflation.
Manuel Cortes said: “David Brown is being informed that our union must have guarantees that members will not suffer a cut in wages.
“Let’s be clear, our members will not pay the price for Northern’s many failures.
“My letter to Mr Brown specifies copper bottomed guarantees must be made that they will not suffer a pay cut by having a below inflation rise nor be treated any less favourably than other grades within the company.
“Our response to the prospect of any form of pay cuts for our members or them being treated as second class in any way will be a ballot for industrial action.”
A Northern spokesman said: “We have had a number of meetings with our recognised unions and our most recent offer is in line with RPI inflation.
“This offer was rejected by the trade unions with no meaningful counter proposals forthcoming.
“We urge the unions to return to pay talks with a willingness to hold meaningful dialogue with credible counter-proposals.”
The union said that it had not received any written proposal on a RPI increase.
Affected TSSA members at Northern fall into the clerical, supervisory and professional and technical staff grades – which includes staff in all areas of the business from stations, to back office and also engineering.
The union said the 2018 pay settlement was decided in September last year, at 3.9per cent and at the time, Northern promised talks on this year's settlement would start in plenty of time to be completed by April 1, but this did not happen.