A SENIOR Labor MP has publicly questioned his own government's continued alliance with the Greens and called for Labor to take them on or risk shedding more votes to the minor party at the next election.

Chief government whip Joel Fitzgibbon said the government was now at risk of permanently losing voters to the "fringe party" unless it rethought its strategy of coalition with them.

Accusing the Greens of abandoning moral principle by blocking offshore processing for asylum seekers in parliament last week, Mr Fitzgibbon has suggested that the party is playing Labor for mugs.

While many in the Labor caucus are frustrated by the deal Julia Gillard signed with the Greens to form government in 2010, Mr Fitzgibbon is the first senior member of the government to openly call for the party to take an aggressive stance toward their coalition partners and "tackle them head on".

Writing exclusively in The Daily Telegraphtoday, the Hunter MP and former defence minister said the Greens' refusal to adopt offshore processing would result in more deaths at sea and greater profits for people smugglers.

"(The Greens) remain the only parliamentary group able to claim an unwillingness to compromise on a matter involving human rights and, indeed, human life," he writes.

"Those of us with greater responsibilities can afford no such luxuries."

Mr Fitzgibbon's anger with the Greens echoes the frustration privately expressed with many Labor MPs who believe that Ms Gillard should tear up the agreement with them.

Greens leader Christine Milne said at the weekend: "When nobody has all the power, everybody has got some, and so every party has to work together and try to work out ways of dealing with complex issues.

"We have an arrangement with the Labor Party because it is a minority government - that's what the people of Australia returned after the last election - and the Prime Minister is governing and the result is that we're getting a lot of legislation through the parliament," Ms Milne told Sky's Australia Agenda.

"And, contrary to the views people have, we're negotiating all the time on good outcomes."

Originally published as Labor MP questions Green alliance