The lawyer for the families of the Pike River Mine victims says new footage reinforces the call for re-entry to the mine.

Footage has emerged of a robot inside the drift of the mine just months after the explosion in 2010.

Workers in breathing apparatus can be seen sticking cardboard onto the robot before it moves along the access tunnel.

Nigel Hampton QC told Newstalk ZB's Chris Lynch the footage shows re-entry is possible.

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He says the Government, Solid Energy, the families and experts from both sides should sit down and begin nutting out a proper staged, manned re-entry.

Earlier, the father of one of the men killed in the disaster said the families 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.

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.

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.

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."

Leaked footage of the inside of the Pike River coal mine does not change the Government's position on re-entry, Prime Minister Bill English says.

English revealed this morning he was unaware of the footage until last night, when it was broadcast on Newshub.

Families of the 29 miners killed in the mine are angry that they were never shown the footage taken by a robot inside the Pike River drift six years ago.

It was filmed three months after the final explosion, and shows two Mines Rescue wearing breathing apparatus working alongside the robot.

The families say the footage backs their long-held view that manned re-entry is possible.

But the Prime Minister says he will not break the law, despite being under pressure for a manned re-entry of the mine.

English told Newstalk ZB's Mike Hosking this morning the footage changes nothing, as any decision to go into the mine has to be made under work and safety regulations.

He told Hosking there had been no cover up of the disaster.

Speaking to Radio NZ this morning, English said he was unaware of the footage until last night, when he saw it on the news.

There was no reason why the families should not have been shown the video earlier, he said.

Police controlled the mine at the time the video was taken, and told Newshub the footage was not supplied to families of victims or the Royal Commission because it was assessed as having no evidential value

English said police had told him that the workers seen in the footage were in the mine's portal, not in the drift.

It did not change the Government's position that re-entering the mine was too dangerous, he said.

"The assessment has to be made by the people who are in control of the workplace and the employees," he said.

"It's their judgment in the end about whether it is safe because if people go in there and they die because of an explosion it is absolutely clear who would be responsible," he said.

Labour and New Zealand First were "silly" for suggesting otherwise, English said.

Police, in a statement, say they believe the men in the video were standing at the entrance to the drift and operating the robot by remote control.

"No one was allowed to enter into the drift as part of the robot operation."

The footage, which is hours long, was assessed as having "no evidential value" and wasn't released, Detective Superintendent Pete Read said.

Additional reporting - NZ Newswire