Around 800 GMB union members at Jacob’s Biscuits Factory in Aintree, Liverpool, began a two-day strike last Sunday.
Workers voted by 84 percent to hold a series of two-day strikes leading up to Christmas.
United Biscuits was recently purchased by Vildez.
Vildez is a holding company of the Turkish manufacturer Ulker, the third largest manufacturer of biscuits in the world.
Strikers are angry about changes that include the suspension of sick pay, new absence management methods and a shorter Christmas break.
The firm wants to use a points system, known as the Bradford Scale, that gives a higher score for staff who take frequent short absences.
Union organiser Steve Fegan said, “It’s a tool to dismiss people quicker”.