The chair of Housing New Zealand says she will not resign over the methamphetamine hysteria scandal.

Photo: Katy Gosset/RNZ

Housing New Zealand's (HNZ) chair Adrienne Young Cooper would not be interviewed but said she will not resign.

HNZ chief executive Andrew McKenzie also again refused to be interviewed.

Housing Minister Phil Twyford apologised this morning, saying he was doing so because the opposition was too cowardly to do so itself.

He accused National of playing along with the "hysteria" of meth and demonising state housing tenants.

The National Party has hit back at the claims it was "gutless" for refusing to say sorry to those wronged by years of meth testing hysteria.

National leader Simon Bridges said Mr Twyford's apology was insincere and people deserved better.

"Just a straight simple apology would have been the right thing for a minister of the Crown to do," Mr Bridges said.

When asked why he wouldn't apologise for National's role in the saga, Mr Bridges said its ministers were following the best scientific advice available at the time.

"We asked the Ministry of Health and Housing New Zealand (HNZ) for the best advice and evidence," Mr Bridges said.

"We did that persistently and we got answers that we thought were authoritative.

"I don't know what more we could have done in those circumstances."

Mr Twyford said the National ministers could have asked the Prime Minister's chief science advisor Sir Peter Gluckman to carry out this research at any point.

"They never bothered to do that - it took me two weeks in the job," Mr Twyford said.

Mr Bridges said it was "easy to say that" but officials had a very different position then than they did now.

As early as 2016, experts were questioning the standards being used by HNZ.

In October 2016, RNZ revealed the Health Ministry had repeatedly told HNZ it was misusing its guidelines - though HNZ later denied that.

Mr Bridges' predecessor and former prime minister Bill English also declined to apologise for the saga and wouldn't say whether his former colleagues should do so.

"The people who succeeded me can deal with that," Mr English said.

He repeated Mr Bridges' comments that National had been relying on official advice.

"It would've been unprecedented for the minister at the time to overrule the official advice ... which actually said it's dangerous to put people in houses with this level of meth," Mr English said.

But Mr Twyford said HNZ reflected the attitude of the government of the day and relied on its guidance.

"Barely a week went by when Paula Bennett was the minister that she wasn't out there demonising state house tenants ... because it polled well," Mr Twyford said.

A report this week from Sir Peter Gluckman found no real health risk to humans from living in a house where meth had previously only been smoked.

That meant hundreds of tenants were wrongly booted out of state houses and millions of dollars wasted on clean-ups.

Sir Peter said there had been an inexplicable leap in logic resulting in clean-up standards for meth labs being used as a measure for passive exposure.