A spokesman for Northern said: “Northern has offered over 5,000 employees a guaranteed, above inflation pay rise over the next three or four years. The offer is a two percent increase in year one, followed by Retail Price Index (RPI) plus 0.1% in each of the following two or three years.

“We are disappointed to have now been notified by RMT that it intends to ballot its members following the negotiations in which the pay increase was offered.”

The spokesman added: “We firmly believe the offer made during negotiations was good for our employees, providing wage increases and stability against a backdrop of wider financial uncertainty. We remain committed to investing in our people and working towards a satisfactory conclusion.”