The Engineering, Printing & Manufacturing Union says the Government and police were unrealistic about how difficult it would be recover the bodies at the Pike River Coal mine and have ended the operation for financial reasons.
Twenty-nine men died in a series of explosions which began at the West Coast mine on 19 November last year. Pike River Coal was placed in receivership on 13 December.
The mine is being handed back to receivers PricewaterhouseCoopers who have until 5pm on Monday to decide on its future.
The EPMU says experienced miners knew the recovery operation was going to be a lengthy and costly exercise.
National secretary Andrew Little, who is also president of the Labour Party, says there were always doubts about whether police would see the operation through to the end.
Mr Little questioned comments by Energy and Resources Minister, Gerry Brownlee that ending the operation was not about money.
Mr Little says the Government - through the police - is leaving the receivers to make a decision it does not want to be accountable for.
Meanwhile, the Council of Trade Unions is questioning whether it is legally possible for the receivers to continue the recovery operation.
CTU president Helen Kelly says the receivers can spend money recovering the bodies only if it is a consequence of resurrecting the mine.