National's Alfred Ngaro is calling for the Hepatitis Foundation's board chairperson to resign.
RNZ revealed this week that the Hepatitis Foundation spent more than $128,000 on travel for its board chairperson, Chris Cunningham, in just over two years and paid for lavish dinners at top Auckland restaurants.
The foundation has received millions of taxpayer dollars through the Health Ministry.
Mr Ngaro - National's spokesperson for the community and voluntary sector - said in light of the investigation into the foundation, it was time for Mr Cunningham to step down.
"I think under the current report, I would see it being very difficult for him not to make a decision that actually his tenure may have come to an end, and I think in this case he should make the appropriate decision to step down, he said.
Mr Ngaro said people would be disappointed and there should have been some accountability.
He said all charitable organisations were accountable to the Charities Act.
"The key principles of the act is to firstly promote public trust and confidence in the sector and the second is to encourage and promote the effective use of charitable resources," he said.
"On those two counts it just seems that this report calls those principles into question by the Hepatitis Foundation."
Mr Ngaro was the minister in charge of charities while the investigation into the foundation was under way, but said he had no knowledge of it at the time.
The two-year investigation by government-run regulator Charities Services was kept secret for more than a year.
It found excessive expenses and gross mismanagement may have occurred, though the foundation told RNZ there was no evidence of any wrongdoing.
Former chief executive John Hornell told RNZ's Morning Report yesterday the people feeling the impacts of the "excessive" spending the most were people in New Zealand living with Hepatitis C.
"That money could have paid for another one and a half nurses on the ground, it could have paid for another three clinical staff in the office, it could have helped ... some people with Hepatitis C when the drug wasn't funded by Pharmac."
Mr Hornell is also calling for Mr Cunningham to resign.
He said when he started working at the foundation there was no money and it was bankrupt. He left the foundation in 2015 after 18 years - 13 of those as its chief executive.
"With careful planning and hard work we built up a portfolio, we got contracts from the Ministry of Health [and] at the time the current trustees didn't get paid for [their work]."
When the money came in, the trustees wanted a salary, Mr Hornell said.
"The dinners were launched on to the back of board meetings at the end of the year. Now, I can assure you, these were top-notch restaurants around Auckland and some in Wellington, spouses and partners of these trustees also attended these meetings."
He said he had attended the meetings and dinners, saying he always felt uncomfortable about them, but never refused to go.
He said they were attended by about 18 people.
"I was the one with the credit card that had to pay for it.
"I think some people just had their snouts so far in the trough they couldn't see the daylight, putting it bluntly."
Health Minister David Clark said the report's findings were "concerning" but would not comment on whether he thought Mr Cunningham should resign.
Mr Cunningham has not responded to calls and approaches from RNZ.
Charities Services, which falls under the umbrella of the Department of Internal Affairs, has ignored RNZ's emails requesting an interview.