Mr Hampton said Pike River Coal Ltd "failed abysmally'' to protect its workers underground, and the Department of Labour had allowed it to happen.
"It is from that position that the union says, on behalf of any underground workers in the future ... how can they, why should they, have any faith in the Department of Labour in the present set up?''
The new acting chief mines inspector Gavin Taylor, from Australia, had shut down the Spring Creek Mine in his first three months on the job, and that suggested it was the people and the culture, more than the regulations, that were at fault.
Council of Trade Unions (CTU) president Ross Wilson said the Health and Safety in Employment Act should be changed to introduce a criminal offence of corporate manslaughter.
"It's about bringing home to employers at a corporate level that there is a major responsibility which they have, and this might result in some leadership being generated at a board level.''
Mr Wilson told the commission the Department of Labour had forfeited its right to be the mining regulator.
The CTU wanted a new specialist Crown agency created for workplace regulation, and did not want the regulator swallowed up in the new 'super-ministry' the Government was creating.
It also wanted a return to the check inspector system, which Mr Wilson said had worked well in Australia and the United Kingdom - and also in New Zealand prior to the 1992 changes.
Mr Wilson said research in the United States showed that the larger the regulator's budget, the lower the rate of mining fatalities. Minor changes to existing health and safety levies could fund such a new regulator.
Families 'determined as ever' to get 29 home
The Inquiry also heard today that rhe Pike River Mine families recently asked themselves whether it was "time to let go'' but were as determined as ever to get their men back.
Families' lawyer Nicholas Davidson, QC, said that since the police decided to hand the mine over to the company receivers 14 months ago, no one had carried responsibility for recovering the remains of the 29 victims.
The families had heard and confronted the refrain that it was "time to let go''. But they had also seen footage of a body lying deep underground, which steeled their resolve to get their loved ones home.
Their patience had been well and truly tried, Mr Davidson said.
The families' lawyers also told the commission that things were wrong from the inception of the mine.
There was poor geological knowledge, and delays meant the mine was running out of time before coal had even been reached.
The ventilation shaft collapsed, unsuitable machinery was purchased, and there was an inadequate pre-drainage methane regime.
The underground fan was commissioned before a risk assessment, and a second escapeway, tube bundling gas system and fresh air base were not prioritised. No external agency had questioned the mine design, which was constantly changing, and the inspectors seemed to be "powerless bystanders''.
The board expected senior managers to create a safe mine, but failed to check this happened, families lawyer Jessica Mills said.
Mine managers kept turning over, and former Pike River chief executive Peter Whittall deferred to manager Doug White.
"By late 2010, the only option would have been to stop Pike River extracting coal, but no one had the resolve to do so.''
The mine's former health and safety manager Neville Rockhouse, who lost his son Ben in the tragedy, submitted today that mines should not even be allowed to operate until key safety plans had been approved by independent regulators.
He use was not at the Greymouth hearing today, but his lawyer James Rapley said Mr Rockhouse had told the truth, and in real and graphic terms spoken of the pressures he and others were under because of the need to mine coal.
Many well intentioned people recognised there were problems at the mine, including the second escapeway.
"Almost on every occasion it was decided the situation was far from satisfactory but the mine would continue operating. It seems at no point was it ever suggested that work would stop.''
Mr Rockhouse said he believed a mine should not be allowed to operate until key plans have been developed, filed and approved by the Department of Labour.
At the beginning, almost everyone had the right safety attitude, but as time went by attitudes changed due to production issues, he said.
Mr Rapley said Mr Whittall and the other Pike River Coal directors accepted no blame or responsibility for the disaster.
Mr Rockhouse had been "bullied and intimidated'' by Mr Whittall, and that was a contributing factor to the tragedy, he said.
The hearing was told Mr Rockhouse also supported a return to check inspectors.
