Philip Routhan, who was sacked from his role with the Plumbers, Gasfitters and Drainlayers Board last year, made the claim at an Employment Relations Authority meeting yesterday. Mr Routhan is before the authority fighting to get his job back.
He alleged he was asked to lie to Building and Construction Minister Maurice Williamson about safety problems at the request of board chairwoman Hazel Armstrong, which she denied.
Mr Routhan said he discovered a large number of gas certificates, which must be returned to the board by a certified gasfitter after work is done, were being returned with serious irregularities and were not being followed up.
According to his written evidence, in one case a gasfitter had requested 572 certificates, but an investigation showed only 290 were returned. Forty-four installations were found to have been put in by a person without a licence, with 33 determined to be "high risk".
Six months after becoming aware of the problem, Mr Routhan received a complaint about a gas explosion in a fish and chip shop in Nelson, where the roof had lifted and the front window and rear wall had been blown out. After investigations, more problems were discovered.
A third investigation into another gasfitter revealed 113 illegal installations.
Mr Routhan told the hearing he was making the information public because he was certain someone would be killed. "Somebody is going to die because of this, and I make this statement clearly in public today: somebody is going to get killed because of this."
Mr Routhan also claimed Ms Armstrong asked him not to tell Mr Williamson when he had briefed her about the problems. He said she knew what questions Mr Williamson was going to ask, one of which was when the board had known about the issue, and asked him "not to drop me in the sh*t".
Mr Routhan said he was uncomfortable with lying to a Crown minister, but Mr Williamson did not ask the question.
Ms Armstrong admitted making the request but said it was taken out of context. She said she had only been told in passing on the street and had not realised the seriousness of the situation. "It was not intended to mislead the minister or withhold accurate information from the minister."
The board fired Mr Routhan last year after he took more than 4000 documents from the board office. He said the papers included 761 gas certificates dating from 2005 that proved his claim.