Labour wants a select committee inquiry into the failure of Solid Energy, so it can subpoena the company's former boss Don Elder to answer questions.
Dr Elder, who resigned last month, was absent from parliament's commerce select committee on Thursday for Solid Energy's financial review, despite still being paid his $1.3 million salary, or $25,000 a week, for a two-month transitional role.
Newly-appointed chairman Mark Ford was unable to answer questions on the company's $389m debt - and Labour's state-owned enterprises spokesman Clayton Cosgrove says a full inquiry is needed.
However, launching an inquiry relies on the support of the National Party majority sitting on the committee.
He says National MPs have been obstructing the commerce select committee - not to protect Dr Elder or Solid Energy, but to protect State-Owned Enterprises Minister Tony Ryall.
Mr Cosgrove believes Mr Ryall knew more about Solid Energy's financial woes than he let on.
"Tony Ryall has been receiving month-to-month reports on this company ... Tony Ryall knew about this, did absolutely nothing about it. They have a no surprises policy, it was described in detail at the committee," he told Radio New Zealand.
Mr Cosgrove added that the government has known about Solid Energy's situation since it carried out a scoping study as part of its asset sales programme in 2011, but still let the company pay out $23m in bonuses.
He says Mr Ryall, Finance Minister Bill English and Economic Development Minister Steven Joyce met with former Solid Energy chair John Palmer in August last year, and they should have been told about the company's finances at that meeting.
Mr Joyce says he has no recollection of the meeting, and would have to check with his office about it.
He added that the government's mixed-ownership model plans for four power companies - including Solid Energy - would mean far better monitoring of their finances.
Mr Joyce says he has no opinion on a potential select committee inquiry.