The Mental Health Foundation wants reassurance from the government that mental health reforms won't be slowed down by the major health restructure.
New data provided to RNZ show national wait times for non-urgent mental health and addiction services over the last two years have risen across all age groups.
As of April last year, more than 1700 patients were seen by mental health providers compared to 2018.
The percentage of patients seen by mental health providers within three weeks dropped from 78 percent to 75 percent and those who took more than eight weeks to be seen jumped from 6 to 9 percent.
Non-urgent wait times for offenders with mental health issues and for people needing support related to drugs and alcohol also stretched out last year.
National Party mental health spokesperson Matt Doocey, who collated the figures, described them as "alarming".
"We're seeing less people accessing services and a longer wait for them to access that service at a time where we've been told by the government of large amounts of investment into our services. It's clear it's not working."
Doocey said local MPs were constantly contacted about mental health services from families.
"That's heart wrenching, they can't access the services that they need.
"We hear from mental health professionals who are telling us that even with the government's announcement of mental health funding, they haven't seen the money flow into the mental health system yet."
The Mental Health Foundation's Sophia Graham had similar concerns and warned people could be waiting longer for support than the data suggested.
"People will have an initial consultation to assess the need and then they go back onto a waitlist to get the support that they need.
"So knowing that people are waiting a long amount of time to get that support that they need is really concerning, particularly given the level of investment that has been given.
"It's showing that there are a higher number of people that need support, and that the system is not responding to that need," she said.
Graham said the foundation had not been told how the planned health system changes will impact reforms to mental health services.
"What we're looking to see in the next few weeks and months is how these reforms will impact the mental health system and how this is going to impact the implementation of He Ara Oranga, which is the government's inquiry into mental health and addiction.
"We will be looking to see that this doesn't slow down the reforms," she said.
'Changes will help us push hard' - Andrew Little
Health Minister Andrew Little said the increasing waiting times were worrying, but the government is only two years into a five-year programme and funding going into the sector is ramping up.
"More money will go into the system next year and more again the following financial year.
"So concerning as it is, I'm confident that the investments that we're making will continue to have a positive impact."
He said pressure was already starting to alleviate at the more serious end of mental health needs.
The minister was confident next year's scrapping of the 20 DHBs and replacing them with a single entity, Health NZ, would not slow down progress on mental health reforms.
"If anything, actually, the changes will help us to really push hard on getting the rollout going.
"We won't have to negotiate with 20 different DHBs, Health NZ will take responsibility and can instruct and direct," he said.
He said officials would continue to engage with mental health groups in the lead up to the changes.