Workers from the North West Ambulance Service are set to take part in two strikes next month.
Unions say the 24-hour walk-outs are scheduled for January 11 and January 23.
Staff are taking industrial action over pay and and staffing.
Paramedics, technicians and call handlers took their first industrial action on Wednesday and are set to strike again on December 28.
The unions claim the Government has declined to negotiate over pay but Health Minister Steve Barclay said paying ambulance staff more would take cash away from frontline services.
