Private certifier Lyall Dix was only months away from a string of fines and suspensions when he signed a construction certificate for the 59-unit Landmark building at Charlestown in March, 2008.

Four years later he was disqualified, as Landmark unit owners confronted the extent of serious defects in their building, likely repairs in the millions of dollars, and the lack of options available to hold anyone accountable.

Mr Dix has been fined, reprimanded and suspended more than any other private certifier in NSW. Building Professionals Board decisions show he approved buildings that were "a hazard to the health and safety" of the people in them, and misled the Board in 2011 after a complaint involving fire safety requirements at a Mascot unit site.

But as a certifier with a bad history he represents just one failure in a failed system of building industry regulation, said Lake Macquarie MP Jodie Harrison and Landmark unit owner Aidan Ellis.

"Dix is just one part of the Landmark's problem. The certifier plays an important role, but the phoenixing of companies so they can walk away when things go wrong is the much bigger issue that really needs to be addressed," said Mr Ellis, who has campaigned for unit building reforms since 2013.

Ms Harrison said the NSW Government had "taken its eye off the ball" on building regulation for many years and the string of scandals related to evacuated unit buildings left people "feeling very uncertain about investing in high density property".

"Shonky certifiers" were just one part of a huge problem, she said.

"I feel sympathy for anybody who buys anything they think should be of a certain standard, only to find that it's not and there's little they can do about it."

A NSW parliamentary inquiry into building regulation, which heard evidence from Landmark unit owner Richard Devon on Monday, was told Coalition and Labor state governments have received 18 reports in the past 20 years urging building industry reforms.

"The time is well and truly past when piecemeal tinkering with the system can suffice," said Michael Lambert, author of a 2015 review of NSW building laws that strongly urged significant reforms, including to the regulation of private certifiers.

Ms Harrison and Swansea MP Yasmin Catley have criticised the NSW Government for failing to put in force legislation passed in 2018 to more tightly regulate private certifiers, including imposing jail terms and fines of up to $1 million for certifiers who issue false or misleading building certificates.

"It's legislation to prevent conflicts of interest involving certifiers, with new rules for compliance and jail terms of up to two years, but it's been sitting on the shelf for 10 months," Ms Harrison said.

Lyall Dix had already been fined and cautioned four times in 2009 before the Board fined him $1000 in October that year for certification failures at a Pokolbin winery.

He was fined, reprimanded and suspended twice after five appearances before the Board in 2011, including certification breaches relating to an Erina Heights supermarket, fire safety issues at Mascot and Blacktown unit blocks, and changing roof and wall materials at a Dee Why apartment building.

Documents show Mr Dix held the key role of principal certifying authority for the Landmark building, signing off on construction, occupation and fire safety certificates to Lake Macquarie Council in 2008.

At the same time the Building Professionals Board was investigating Mr Dix's issuing of an occupation certificate for a 72-unit Mount Druitt project that relied on fire safety certificates, where the Board found fire safety requirements were not addressed.

An Administrative Decisions Tribunal backed the Board's finding in August, 2009 that Mr Dix was guilty of unsatisfactory professional conduct after five allegations of incompetence were proven.

By November, 2009 Landmark unit owners at a strata annual general meeting voted to engage a building consultant to provide a full report on "identified and other defects found" in the building, only months after residents moved in, and after the NSW Master Builders Association gave the Landmark an excellence in construction award.

"The property has to date reported numerous defect listings and building defect reports," minutes of the meeting said.

They noted builder Kingston Properties, under director and Hunter builder Peter Durbin, had "failed to provide a rectification plan despite the many reports and negotiations to the building and development section of the Kingston business".

The strata committee also voted to "pursue rectification with Kingston Properties and external parties as required".

Mr Durbin wound up his two companies associated with the project after legal action by the 59 unit owners.

In an interview with the Newcastle Herald Mr Durbin did not deny the Landmark had defects, but said the "ambit of the claim" pursued by the unit owners in court was such that his building company "could not continue to meet the expense associated with responding to it, and the company therefore entered into liquidation".

In a statement on Tuesday the Newcastle office of Dix Gardner, a company started by Lyall Dix, distanced itself from the operations of other Dix Gardner offices in Sydney, Brisbane and the Gold Coast.

Dix Gardner Newcastle managing director Scott O'Donohue said his office had been a separate entity for five years.

"Each individual private certifier by law must make their own decisions, approve, inspect buildings while being ethical and law abiding. It's actually not rocket science to follow the law and procedures set out in the Environmental Planning and Assessment Act and Regulation, and end up with a building suitable for occupation," Mr O'Donohue said.

He was "not privy to any of the alleged issues/allegations/findings regarding Lyall Dix or the Dix Gardner Group Pty Ltd".

"I am of the opinion that there should be stronger penalties for those private certifiers who intentionally bend or break the rules," he said.

Ms Harrison said the NSW Master Builders excellence in construction award to the Landmark in 2009, as people living in the building were reporting serious defects, "says that the whole industry needs to be better regulated, which is what we've been saying".

Mr Dix did not respond to requests for comment.