Progressive Party leader Jim Anderton says members of the party can now join the Labour Party as well.
He says the two parties have formed a coalition in opposition and Labour's ideas are compatible with that of the Progressive's.
Mr Anderton is a former president of the Labour Party who quit to form a group called New Labour. This subsequently became part of the former Alliance Party and he now heads the Progressive Party.
He says any party members who don't want to join Labour do not have to.