National MP Simon Bridges says he voted against legalising pill-testing at festivals because ecstasy deaths went up in the UK after it approved testing.
But academics who've studied the effect of pill-testing and the testing bodies say it's saving lives, blaming the rise in deaths on the sheer potency of drugs sold in the underground market these days.
New Zealand this week legalised festival pill-testing for 12 months, with every party in Parliament but National giving it the nod.
"The Government is committed to minimising drug harm and to treating drugs as a health issue - I make no apology for prioritising young New Zealanders' safety this summer with this law change," said Health Minister Andrew Little.
Appearing on The AM Show on Friday, Bridges said the change would encourage kids to do drugs.
"The Labour Party view that we heard in the Parliament, I sat through the whole debate, was that 'look, it's happening, it's on us, we should go with it and it would be safer'.
"But I've looked at the evidence. It seems to me what's quite clear is if you test you give a false confidence; that results in more use and more harm."
He said in the UK, deaths "went up pretty significantly as a result of this".
"One of the things people think is, you get rid of the bugs and the impurities - yep, you do do that; but the reality is with MDMA or E deaths, is the ecstasy - sometimes with other stuff with booze and the like - but it's the ecstasy that's doing the killing."
Drug-testing agencies have been allowed to operate at festivals in the UK since 2016. That year, there were 63 Ecstasy-related deaths in England and Wales in total - not just at festivals - only about half of which could be attributed to ecstasy alone.
The following year the total death toll dropped to 56. In 2018 there were 92, and in 2019, 78.
The experts behind the Global Drug Survey warned in 2016 ecstasy was becoming dangerously potent - some pills containing up to 300mg of MDMA, the psychoactive ingredient which gives ecstasy its kick. This is about three times stronger than the historical dose found in pills.
"If you're 17 or 18 and just starting to use these drugs, you could actually get a very strong product which could lead to overdose," Monica Barratt from the National Drug and Alcohol Research Centre at the University of New South Wales said at the time.
Trevor Shine of UK drug testing body TicTac told BBC News last year, when the record-high 2018 statistics were released, potencies had risen over the years; and Ian Hamilton, a senior lecturer in addiction and mental health at the University of York, agreed.
"People have been caught out by the strength of some pills that have made it into festivals and music venues - some have contained more than 200mg of the chemical MDMA... That's something that would catch out an experienced user as well as a naive one."
Ecstasy deaths in England and Wales in the early to mid-2000s - before festival testing was commonplace - were regularly in the 40s and 50s.
One festival, the Secret Garden Party, reported a 95 percent drop in drug-related hospital admissions the year it introduced pill-testing. One-in-five substances sold that year brought in for testing were found to be something else entirely - ketamine, anti-malaria medication, pharmaceuticals, sugar and plaster of paris were all sold as ecstasy or cocaine. Similar results have been recorded at festival checks in New Zealand, operating somewhat outside the law.
The rise in ecstasy-related deaths could also be a part of a larger trend, rather than linked to festival testing. 2019's 78 ecstasy-related deaths in England and Wales were just a fraction of the total deaths due to illicit substances - 2917 - the highest since records began in 1993.
One UK drug policy researcher calculated the annual risk of using ecstasy was "broadly equivalent" to that "posed to participants by motor sports, water sports, mountain hiking, being a road user, giving birth, liposuction, taking antidepressants and being in police custody", and lower than those who drink alcohol, do cocaine and take part in motorcycle racing.
During the debate over cannabis legalisation ahead of this year's failed referendum, advocates for change said taking drugs out of the black market would allow users to know exactly how much they are consuming - much like how alcohol drinkers do.
Labour MP David Parker, appearing on The AM Show with Bridges, said harm prevention worked - comparing festival testing to New Zealand's needle exchange programme. A study earlier this year found that world-first initiative, which began in the 1980s, prevented an epidemic of HIV amongst intravenous drug users.
"We've had needle exchange programmes forever to minimise harm - and it's worked. It hasn't increased drug use, it has reduced the harm - and this is the same principle."
Ultimately, Bridges said "two wrongs don't make a right", urging people not to use drugs in the first place.
"Don't do it. If they do, okay. But the reality of the testing... this Bill with some other stuff that happened last year is a move down towards a wholesale liberalisation of drugs. Andrew Little in effect said that himself."
The temporary law is expected to be replaced with something more permanent this time next year.