This week, provisional statistics from the Chief Coroner put the national suicide rate at the highest level since records began, with Maori, Pacific and young people particularly affected.
Doocey said having former Blues coach and All Black Kirwan there added weight to the effort.
"He's one of the most important and relevant people speaking about mental health," Doocey said.
"When you get the right person to come out and say: 'It's ok because I've been there', a lot of people who would not before have asked for help are now asking for help."
Doocey spent 15 years in London working in the mental health sector, and said New Zealand's three-year political cycle produced a lack of commitment to some solutions.
The group wants to take advice from experts and politicians, and come up with long-term suggestions that will out-last individual Governments.
"There's a huge demand growing. And we need a longer-term policy setting to start addressing that," Doocey.
Speaking before the launch, Swarbrick said the group was an attempt to de-politicise what were often charged issues, and the result of a two-year effort.
"The best possible thing we can promote with this group is a space for mature and respectful discussion about very vexed, very emotional issues," she said.
"You'll have pretty much all politicians agreeing about what the problems are here, but not necessarily on the solutions."
Swarbrick, who has openly spoken about being on medication for depression, said in her time at Parliament she had been shocked to hear politicians heckle each other using language that stigmatised mental health issues.
"I think that we have to hold ourselves to a higher standard and that's what this cross-party group … offer[s] the opportunity to do."
The joint group comes after similar cross-parliamentary groups on climate change and women's issues.
