Progressive Party leader Jim Anderton says the Pike River mine tragedy raises questions about whether mining is safe enough to continue in this country.
MPs paid tribute to the 29 miners and their families on Thursday before Parliament rose early, as a mark of respect.
Some party leaders say now is the time for mourning and questions about what exactly happened at Pike River can wait.
But Mr Anderton says the longer term questions about the future of mining in New Zealand will have to be addressed at some stage.
"This kind of accident and the deaths resulting from it, is unacceptable," he said.
"If we can't find out what happened, we should question if we should continue putting people in harm's way like this."