Pike River Coal chief executive Peter Whittall has accused police and other officials of withholding information about a fire burning inside his company's explosion-hit West Coast coal mine.
Not knowing about the fire contributed to his optimistic statements to families on the chances there were survivors inside the mine, he claimed.
Mr Whittall is giving evidence to the Royal Commission of Inquiry into the loss of 29 of his workers in the Pike River mine disaster.
Under questioning from counsel for the Pike River families Nicholas Davidson, he conceded there was only ever a faint hope the trapped men were alive.
To survive, the men would have had to have walked to the upper reaches of the explosion-hit mine before constructing a brattice shield and sucking air from a compressed airline, he said.
Mr Davidson said that "just doesn't add up" and was an extremely faint possibility.
Though Mr Whittall agreed it was a slim hope, he denied deliberately giving false hope to families.
"Human beings are marvelous creatures aren't we and this does happen on occasion, albeit slim hope."
Mr Whittall said his statements were partly shaped by the "embarrassing and downright extraordinary" fact he did not hear about a fire inside the Pike River mine until the inquiry.
He said police had access to reports from former mine inspector Robin Hughes which said there was a fire in the mine, but did not pass that information to him.
Not having those reports helped shape his optimistic messages to families about the possibility groups of miners were clustered around a fresh air line.
"When I stood up there and said this is the truth, it was certainly the truth as I knew it," he said.
Mr Whittall said at one point, Prime Minister John Key advised him to stop talking about "heating" inside the mine and start talking about fire.
He was surprised at that, as he had no information about fire in the mine.
His role communicating with families meant he should have been as well briefed as police superintendent and incident controller Gary Knowles, he said.
"It's starkly apparent that I was not so briefed.
"As I said before quite embarassing and downright extraordinary that it never got to me. I have no idea why that was not raised... It was extraordinary that I should learn about it at this commission and at no time before that."
Mine boss breaks down
Earlier, Mr Whittall broke down while telling families of his immense regret at the way he told them their loved ones were dead.
But he rejected allegations he lied or gave families of false hope after an explosion in his company's West Coast mine on November 19.
He repeatedly paused to clear tears as he recounted a disastrous meeting where families were told of the deaths of their loved ones in a massive second explosion on November 24.
Many family members cheered and clapped when Mr Whittall started the meeting with earlier news of rescue teams kitting up to go into the mine.
The room had to be quieted before he announced all the men were dead.
Under questioning from Pike River Coal counsel Stacey Shortall, he said he had regretted the way he broke the news every day since the second explosion.
Getting to the meeting and seeing families milling around was very difficult, Mr Whittall said.
"Because I knew. Because I knew the second explosion had occurred and I knew they didn't know."
He was extremely upset at the time and struggled to find the best way to relay the news.
"I felt nauseous. I felt sick. I didn't know what to say. I felt a bit overwhelmed and intimidated."
Mr Davidson said the way Mr Whittall had broken the news of the deaths to families had left many of them with a scar that had not healed.
He said it was "the most insensitive thing that could be done to them."
Seven family members of some of the 29 men who died yesterday accused Mr Whittall and police of giving them false hope and withholding information in the wake of the first blast.
Mr Whittall told the inquiry reading those statements was devastating.
He had only been able to read one or two a week because of the emotional toll they had taken, he said.
"If anyone had their tragic suffering made worse by thinking I gave false hope... then I'm sorry they felt that.
"I've gone over it in my brain for 10 months. Every day and every night... There was an opportunity I believe for some men to have survived."
"My only regret is that anyone could at any stage believe that I had anything other than the best intentions to tell the truth at all stages."
He said the hopeful message he conveyed to families was honest.
"Miners are resourceful guys. They're tough and they're strong and they're hardy. I strongly believed that if anyone could have survived, they would have."