Young people are waiting months to get mental health follow-ups after asking for help and a government inquiry into the sector is urgently needed, the Green Party says.

But the government says the figures are the same as they've been for years and work is already being done.

DHB figures show nearly 3300 children and youths - or 26 percent of all youth cases - had to wait longer than eight weeks to get a second appointment after seeking help in the 2014-15 year, Fairfax Media reports.

Green Party Co-Leader James Shaw said those numbers proved an urgent inquiry into the mental health sector was needed.

"Mental health services are struggling all around the country because of government cuts to the overall health budget, and our vulnerable young people are paying the price," he said.

"New figures released by the coroner last week show that New Zealand has the highest youth suicide rate in the OECD, and I think it is unacceptable for young people to be waiting this long to get the help that they need."

The Ministry of Health says it has increased funding for mental health services by about $300 million since 2008 - from $1.1 billion in 2008-09 to 1.4 billion in 2015-16.

READ MORE: Counsellors 'over-burdened' as teen suicide rate creeps higher

But opponents say increasing demand in the sector and inflation mean the budget has actually fallen in real terms.

Health Minister Jonathan Coleman said he didn't agree there was a need for an inquiry.

"Overall the sector provides high quality mental health services for New Zealanders - from prevention, through to primary care and specialist services," he said.

He said nationally, the percentage of child and youth patients waiting more than eight weeks had not significantly changed in the past four years and the government still expected urgent cases to be dealt with within 48 hours.

"Nationally 91 percent of cases are seen in less than eight weeks," he said.

The government was currently evaluating the cross-agency Youth Mental Health Project set up in 2012.

But Dr Coleman said suicide rates were too high.

"Suicide rates have remained consistent in recent years when you look at the population as a whole: 12.32 per 100,000 this year is lower than 12.65 in 2010-11," he said.

The government had put $25 million behind a suicide prevention plan in 2013 and was currently working to develop a new strategy, he said.

Are you affected by an issue in this article? Here's where to get help:

Lifeline - 0800 543 354
Suicide Crisis Helpline (open 24/7) - 0508 828 865 (0508 TAUTOKO)
Depression Helpline - 0800 111 757
Samaritans - 0800 726 666
Youthline (open 24/7) - 0800 376 633. Text 234 for free between 8am and midnight, or email [email protected].

0800 WHATSUP (0800 9428 787), Open between 1pm and 10pm on weekdays and from 3pm to 10pm on weekends. Online chat is available from 7pm to 10pm every day at www.whatsup.co.nz.

Healthline - 0800 611 116
For more information about support and services available to you, contact the Mental Health Foundation's free Resource and Information Service on 09 623 4812 during office hours or email [email protected]

If it is an emergency and you feel like you or someone else is at risk, call 111.