Green Party MP Kevin Hague has taken what he says is the first step towards laying a prosecution against the Department of Labour over the Pike River disaster.
The department has been criticised at the Royal Commission of Inquiry for its monitoring of the mine where 29 men were killed a year ago.
Earlier this month, the department laid its own charges against three parties, including the Pike River Coal company chief executive Peter Whittall, alleging health and safety failures at the mine.
Now Mr Hague has written to the Department asking if it will lay charges against itself, as a first step towards prosecuting it.
He told Checkpoint he had sent a form letter to the department this week and he did not expect to hear back before the election on Saturday.
When he hears back, he says he'll talk to families about what further action should be taken.
Auckland University law lecturer Bill Hodge says such a legal move has not been made before but it is possible and would be a test case.
He says proving the department breached its own rules would be extremely difficult and costly.
Bill Hodge says the case would have to show there was a failure to identify or monitor hazards that led to the explosions at the mine, or were likely to do so.