The Labour Party's attitude to re-entering the Pike River Mine is hypocritical and unsafe, according to the government.
Labour leader Andrew Little has pledged to seek legislation making it easier for the mine to be entered and the remains of the 29 men who died there in 2010 retrieved.
Some of the relatives of the deceased want this to happen and have been blockading the entrance to the mine to prevent it from being permanently sealed.
Solid Energy, which owns the mine, has analysed the risks and concluded entering it would not be safe.
Mr Little met the protesting family members this week and pledged his support.
He promised to seek leave to table a bill on the first day of the new parliamentary year exonerating Solid Energy's directors from liability for any harm to people taking part in re-entry of the mine.
Environment Minister Dr Nick Smith accused Mr Little of a dangerous and contradictory position.
"It would be extraordinary to make an exemption from the Health and Safety at Work Act at the very place where 29 workers lost their lives from inadequate standards that triggered the new law," Mr Smith said.
"This is a bid by Mr Little to outplay [New Zealand First leader] Winston Peters politically rather than taking a principled stand about the importance of a consistent approach to workplace safety."
Dr Smith said his advice showed the mine had 100,000 cubic metres of methane and was likely to have a residual source of heat as well.
This would be capable of triggering an explosion if there was a source of oxygen.
The minister added there was a risk of rock falls from unstable strata fractured by the 2010 explosions.
"There is a significant difference between someone saying re-entry might be possible compared with company directors taking legal responsibility," Dr Smith said.
Mr Little said yesterday that the victims' families were promised everything possible would be done to recover their loved ones' bodies, and the government needed to follow through on that.