Labour leader Jacinda Ardern has given an assurance to the relatives of suicide victims that their voices will be heard when her government reviews mental health services.

She was speaking outside parliament on Sunday at an event marking World Suicide Prevention Day.

Organisers from YesWeCare.NZ had placed 606 shoes on parliament's lawn, each representing a New Zealander lost to suicide in the last 12 months.

The shoes were those of victims, collected from bereaved families in towns and cities across the country.

More than 100 people gathered outside parliament, many of them in tears.

Ms Ardern's voice broke when she began her speech and spoke of the "absolute devastation" the shoes represented.

"For a long time there have been calls for simple things like making sure we do everything in our power in the mental health system to look after those most in need," she said.

"We must make sure we get it right - you will be heard when we review mental health services in New Zealand."

Ms Ardern said she would start as early as possible on her party's policy to place mental health teams in every school.

"We will do everything in our power," she said. "I don't believe in setting a target that is anything other than zero - anything else suggests that we have a tolerance of loss to suicide, and we shouldn't."

* Readers seeking support and information about suicide prevention can contact Lifeline's 24-hour telephone counselling service on 0800 543 354.
Depression Helpline (8am to 12 midnight) - 0800 111 757
Samaritans - 0800 726 666 (for callers from the Lower North Island, Christchurch and West Coast) or 0800 211 211 / (04) 473 9739 (for callers from all other regions)
Suicide Crisis Helpline (aimed at those in distress, or those who are concerned about the wellbeing of someone else) - 0508 828 865 (0508 TAUTOKO)
Youthline - 0800 376 633, free text 234 or email talkyouthline.co.nz
What's Up (for 5-18 year olds; 1 pm to 11 pm) - 0800 942 8787
Kidsline (aimed at children up to 14 years of age; 4pm to 6pm weekdays) 0800 54 37 54 (0800 kidsline)