The father of one of the men killed in the Pike River mining disaster says the families have always believed the Government wasn't telling the truth about mine safety.

The Government has long said high concentrations of methane inside the mine make it too risky to re-enter to retrieve the bodies of the 29 men killed in the November 2010 blast, because the gas could explode.

But footage leaked to Newshub on Sunday showed two Mines Rescue workers inside the mine three months after the explosion, with no gloves, apparently relaxed as they fashioned a makeshift cover for a robot out of cardboard and tape.

The robot is seen to be steaming or smoking well inside the mine, but the workers do not panic and nothing explodes.

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Bernie Monk, whose son Michael was killed in the explosion in the West Coast coal mine, said the newly leaked footage did not come as a surprise.

"This is something we brought to the Government six years ago.

"It's been a complete cover-up right from the word 'Go'," Monk said.

"It's something that we have known about for a long time, but we didn't want to have to go to the extreme of bringing it out in the public ... but after six years we just can't accept the way the families have been treated."

Monk said the footage made clear what the families have long said: That recovery workers could safely go down into the mine to retrieve the bodies of the 29 men killed.

The workers in the video are unconcerned because the mine's atmosphere is almost 100 per cent methane, and at such high concentrations the gas is inert.

"In other words, we could put one of the biggest rockets with engines blowing flames and it wouldn't explode."

The families have hired independent experts who have consistently said that the mine is safe to enter.

The families want to use what they say is an even safer option than wearing breathing apparatus, pumping in nitrogen which would push out the methane before letting in fresh air.

"Then you and I could walk up there without any gear on at all."

Monk wanted all recordings from the mine released.

"All the recordings that were taken at the mine were removed by police and were never, ever shown to the families, but we knew they existed."

According to Newshub police have had the footage for six years but have not shown it to the families or the Pike River Royal Commission of Inquiry because it was "assessed as having no evidential value".

President of the New Zealand Police Conduct Association Shannon Parker has lodged a complaint with the Independent Police Conduct Authority.

She said the media coverage of the footage gave rise to some important questions.

She raised a number of questions including how police established the footage didn't have enough "evidential value" to present at the Royal Commission and what other information police had not provided.

"On the face of it and based on this news story there seems to be little point in having any such inquiries if police are picking and choosing what is being presented based on what they have decided is relevant."

IPCA Manager: Case Resolution, Sarah Goodall, confirmed the complaint had been received.

"In accordance with our normal process we will be assessing the complaint and gathering any information necessary to enable us to decide what action should be taken by the Authority."

Monk claimed the Government had been "completely dishonest" with the people of New Zealand.

"My argument is: Hey Government, step aside, stop lying, stop covering up for the country, let our experts in, we'll get the job done and get on with life."

Acting Conservation Minister for Pike River Issues Nick Smith said from the Government had viewed the leaked footage, but had been advised it was used by Solid Energy as part of its investigation into whether the mine was safe to re-enter.

"The fact remains that is unsafe to do so. As we have repeatedly stated, gas levels beyond the seal are consistently around 100 per cent methane, making a manned re-entry unsafe," Smith said.

"The Government has, however, agreed to work with Solid Energy and the families to investigate the potential for an unmanned entry. This footage is being reconsidered as part of that investigation though that work is ongoing."