The Council of Trade Unions says a move by the Government to alter employment laws will drive wages down and strip workers of their rights.
The council has launched a campaign in Auckland to protest against proposed changes to the Employment Relations Amendment Bill.
The law change would allow employers to walk away from negotiations on a collective contract and in some cases ban strikes.
CTU president Helen Kelly said the change is designed to humiliate working people and would result in lower wages, no tea breaks and greater workplace vulnerability.
"The Government's own papers tell us and tell them that this change will allow employers to walk away from the bargaining. This will mean that collective bargaining will decline - and that is code for wages will fall."
Ms Kelly said unions would hold stopwork meetings throughout the country to rally opposition to the bill, starting in Wellington on 20 August.