Chronic underfunding of the Counties Manukau District Health Board (DHB) has seen it shortchanged by up to half a billion dollars over the past 21 years, according to Labour MP Louisa Wall.
The former MP for Manurewa made the comments during the parliamentary health select committee's annual review of the DHB on Wednesday.
"You have been underfunded by well over $500 million," Wall said.
"You haven't received your fair share, from an equity perspective of the money that the Government allocates to serve the population you serve."
The DHB's chief executive Margie Apa, chairman Mark Gosche and chief medical officer Peter Watson all spoke during the hour-long hearing.
According to Gosche, the 2018 Census undercounted the Counties Manukau population by almost 12,000 people.
Gosche said this has resulted in it being underfunded for a number of years.
That's despite the fact its residents represent some of the most socio economically deprived people in the country, with massive health problems such as diabetes, obesity and heart disease.
"The fact of the matter is Census hits us really hard," he said.
"There's a massive undercounting of Māori and Pasifika people. Our health user data shows there are 12,000 people in Counties Manukau that are unaccounted for - that's $31 million we don't receive."
He said the end result is the DHB has to try and make up for the shortfall.
"We understand the impact of this, but we can't live with it any longer. We've got to have the resources to do the job for the population we've described."
Gosche, who recently said the DHB was expected to post a $29.2 million dollar deficit this year, said the Ministry of Health is more than aware of its problems.
Apa said the area's demographics which put pressure on its operations.
Counties Manukau has one of the fastest growing populations in the country with more than 601,000 people in the area. Two thirds of the population are Māori, Pasifika or Asian.
"From an equity perspective half of that population are living in the poorest households in New Zealand," she said.
Chief medical officer Peter Watson said Counties Manukau has a higher level of obesity than any other DHB in the country, and as a result has higher rates of diabetes, cardiovascular disease and gynaecological cancers.
Last week, Stats NZ said it had failed Māori in the 2018 Census.
"One of the things we need to keep front of mind is that many Māori don't see the value in census for them. Because they don't see the value, or don't trust the system, they don't participate and this means they don't get counted," general manager for census Kathy Connolly said.
"We've learned from the experiences of 2018 and have made changes as a result. These changes are based on advice we received from external reviews and our own analysis of what worked and what didn't. Now, we need to test them to make sure they work."