Finance Minister Bill English is pessimistic about the future of Solid Energy, saying the Government is still trying to find out whether it can be a viable business.
Mr English said the state-owned company had continued to struggle as coal prices had kept falling.
Solid Energy was bailed out by the Government and its banks in 2013 and has a debt of about $300 million.
Despite making changes to its operations, including focusing on mining coal more efficiently, it had not been able to shake off its financial difficulties.
Mr English said there had been ongoing talks with Solid Energy over the past few months but he would not comment on the coal company's negotiations with its banks.
He said the ailing coal company would not get any more money from the Government.
"We've said that for some time. We've done two rounds of support for the company and, you know, in the end...you have to work out whether there's a viable company there or not, and we're in that process.
"So we're doing everything we can to secure the continuity of the company," Mr English said.
Labour Party leader Andrew Little said poor management and appalling government oversight were responsible for getting Solid Energy into the plight it now faced.
But even Mr Little would not promise to spend more money on the coal company.
"I'd want to have a close look at their balance sheet, the state of the business, before making any decision about plunging any more public capital into it."
Mr Little said he was worried about the workers at the coal company.
The Green Party urged the Government to provide proper support for workers if the company failed.
Co-leader Russel Norman said the Government had to help the workers who would be affected in the event of a company collapse.
"The National Party picked a winner - thought it picked a winner on fossil fuels and coal - turned out that fossil fuels and coal aren't such a winner after all.
"So, you know, I think if the company's going to fall over, as seems likely, we need to put in place measures to support the workers involved, because it'll have a pretty significant impact on the community."
Dr Norman said National thought it had picked a winner in Solid Energy, but that the company was operating in a dying industry.