Phil Twyford is defending the Government's inquiry into mental health, saying it's necessary to develop a plan.
National has criticised the nine-month, $6.5 million plan, leader Bill English earlier this week saying "inquiries don't fix things".
"I think they are playing for time. They're actually short of cash to meet the expectations they've created," he told The AM Show.
"An inquiry will take them a year and might give them a bit more time to find the cash to do a bit more, maybe in 2020."
Mr Twyford told The AM Show on Friday "big strides" on attitudes towards mental health have been made in recent years, but the help on offer is failing to keep pace with demand.
"The system's a mess... There just isn't the resourcing there. I know in my patch out in west Auckland, young kids who need mental health help just can't get it."
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The Government made mental health a "big priority" making an inquiry an election promise, and is planning major reform - but first, they want to know what will work.
"Before you start ploughing resources in, you've got to have a good plan."
Health Minister David Clark said a royal commission of inquiry was ruled out as it would take too long.
'Something has to give'
National MP Judith Collins, appearing alongside Mr Twyford, said the Government's running its finances too tight and "something has to give" if it's going to pour more funding into mental health.
"I put a big lot of funding into mental health in prisons because people won't say they have a mental health problem to the same extent as you would say, 'I've got the flu,'" she said, referring to her time as Minister of Corrections.
"We used to lock people up into mental homes, asylums, until the early '90s when the Western world basically emptied them out and said, 'Off you go.' A whole chunk ended up in prisons instead."
She says despite the progress, there is still a stigma that mental health problems are "contagious" and "difficult"
"Actually, it is pretty much a normal part of a lot of people's lives... until we get that collective attitude, we're not going to bring about the changes."
Auckland University law professor Ron Paterson will chair the inquiry, pocketing $1400 a day.