Progressive Party leader Jim Anderton says his party will form an Opposition coalition with the Labour Party.
National was sworn in as the Government on Wednesday after winning the election on 8 November.
Mr Anderton was Minister of Agriculture in the previous government, as part of his coalition deal with Labour.
Labour leader Phil Goff says he plans to appoint Mr Anderton as Opposition spokesperson for agriculture.
Mr Anderton, who is the only Progressive MP in Parliament, says he is pleased to continue his relationship with Labour.
He says he will attend some Labour Party caucus meetings, and will also be on the front bench of the Opposition.
However, Mr Anderton says he will be free to speak on other issues in his role as Progressive Party leader.
Mr Anderton was president of the Labour Party from 1979 until 1984. He resigned from the Labour Government in 1989 and formed the New Labour Party, which merged into the Alliance in 1991.
