Former Labour Party president Andrew Little says free access to worksites by trade union organisers is a fundamental right that should be restored.
It is six months since employment law changes banned organisers from worksites without employer consent.
Unions say that has made contact with members and potential members more difficult.
Mr Little, who was national secretary of the Engineers, Printing & Manufacturing Union and is now a candidate for Parliament, says having a law that thwarts union members' rights to speak to their organisers is ''utterly insidious''.
Business groups say employers cannot withhold consent unreasonably and unions are free to test that in court.
