The Green Party caucus is having mixed success in its first term in Government in the 20 years it has been in Parliament, with one minister and one backbencher scoring highest in caucus ratings today.

But the party's parliamentary wing has a handicap that afflicts no other party to the same extent.

Its own party is its harshest critic and no more so than its former MPs who criticise it publicly on a regular basis.

The problem is exacerbated because many of its ex MPs remain politically active, such as Russel Norman, who now heads Greenpeace in New Zealand.