Instead of negotiating, Unite says managers have initiated disciplinary proceedings against four members of the workforce.
It is understood the claims relate to the occupation of the Merseyside plant on 18th February to try to prevent the company from moving material out of the plant after the initial lockout
Unite officials have also protested against redundancy hearings taking place for six supervisors who it says are being targeted for no obvious reason.
In a statement, the strikers said: “This week and next, further meetings will take place between workers representatives in Mayr Melnhof factories across Europe with workers from MMP UK to gain further backing in our dispute.
“It’s clear that this could very much start hitting the supply chain of major customers such as Kelloggs UK who are supplied by MMP UK directly.”
Watch our video report on the 3-week resistance to the lockout and redundancies here: