David Benson-Pope

David Benson-Pope

Labour could be defending David Benson-Pope to spite National rather than because they genuinely want to protect him, Victoria University political lecturer Jon Johansson says.

Mr Benson-Pope has been the centre of a new swath of allegations relating to his actions as a teacher at Bayfield High School.

It has come out that girls complained about Mr Benson-Pope after he walked into their shower block, and one said he hit her with a ruler.

Last year police found a prima facie case after investigating allegations he assaulted students but decided not to prosecute.

In the past, Prime Minister Helen Clark has been quick to dump ministers in trouble; Dover Samuels, Lianne Dalziel and John Tamihere spring to mind.

Dr Johansson said it was possible she and senior caucus colleagues were protecting Mr Benson-Pope because they did not want National to score a scalp following a tough election campaign.

"There is a real ugliness about our domestic politics at the moment and I think that's part of the context of which perhaps Clark is thinking 'I am not going to give National a trophy here'," he said.

"Whether that's affected a more clinical assessment of Benson-Pope's moral authority to be a Cabinet minister is open to question and once the people start speaking, by way of public opinion polling, that's going to become clearer."

Today in Parliament, Helen Clark fired a warning shot at National deputy leader Gerry Brownlee, saying she had seen material relating to when he was a teacher and cautioned against throwing stones in glass houses.

"Given that the PM has raised this today, that is the nuclear option," Dr Johansson said.

"That is an absolute show of defiance. Certainly the public are the only losers once politicians go down this route."

Auckland University political scientist and Robert Muldoon biographer Barry Gustafson had a different theory.

He said he previously saw the Prime Minister in contrast to Sir Robert, who defended his MPs no matter what.

"Far from defending a minister, if a minister did something that was clearly unwise they took responsibility for it... she did not try ever to defend the indefensible," he said.

He suggested that after Helen Clark was involved in controversies -- over signing a painting she did not create and being a passenger in a speeding motorcade -- she had become more accepting.