Trust leaders say patients could come to harm as between 120 and 130 treatments are cancelled for each day of industrial action at hospitals including Royal Oldham Hospital.

The Northern Care Alliance, which runs Salford Royal Hospital, Royal Oldham Hospital, Rochdale Infirmary and Fairfield Hospital in Bury, said the cancelled care includes cancer treatment.

In recent months, more than 350 staff have walked out in a dispute over overtime payments. The row centres on the use of an outside agency, NHS Professionals, to manage overtime, with Unison saying staff can earn less than they would on a normal shift, with some missing out on as much as £80.

Care is cancelled because regulations around staff walkouts reduce theatre capacity to Christmas Day levels. Christmas Day cover means only trauma care and emergency, or life and limb, operations can be delivered.

Strikes took place for three days this month, as well as in August and in June. Strike action has taken place outside the Royal Oldham Hospital.

Leaders at the trust said they are concerned that too narrow a view is being taken as to what constitutes emergency care. Chief operating officer Leah Robbins told councillors this week that lists including oncology patients are cancelled on strike days and moved to the following week.

She said consultants had tried to explain that while treatment is not life or limb immediately, waiting a couple of days can cause harm to patients.

Chief nurse Juliette Cosgrove said there is a disagreement with Unison about what is required for emergency care, but said the union's current approach is consistent with industrial action legislation.

Unison North West regional organiser Kevin Dolan said members do not want to see treatment cancelled. He said the figures show the trust's failure to resolve a dispute of its own making, not a failure by workers. Ms Robbins added the NCA wants to work with Unison to seek a resolution.