Access Canberra has also been accused of being a "friend of industry" rather than a "feared regulator", as the government agency came under fire during the second day of public hearings at the ACT Assembly's building quality inquiry.

The inquiry was ordered amid widespread community and industry concerns about the standard of building work during Canberra's construction boom.

John Grant, a former chief executive of the Australian Building Codes Board, appeared at Wednesday's hearing to detail his experience with what he described as "third-world practices" in construction and government enforcement of regulation in the ACT.

Mr Grant is the head of the owners corporation at the Kingston Place complex, which last year launched Supreme Court action against Morris Construction Corporation over alleged defects at the 120-home development. The developer has denied it is liable for the allegedly defective work.

Mr Grant said Kingston Place owners had spent about $250,000 on expert reports and almost $400,000 on legal fees since 2014. The owners agreed to pay a levy on top of their strata fees to help fund the legal costs.

He told the hearing that money, time and considerable stress could have been saved had the developer and Access Canberra taken "prompt action" to rectify the problems when they were first identified.

Owners lodged a formal complaint with Access Canberra in August 2016, and Mr Grant said the regulator had twice stated that it intended to order the developer to fix the alleged defects,

Mr Grant said that never eventuated, meaning owners were left with "no other option" but to launch legal action. The proceedings are ongoing.

"This lack of action by the ACT government in responding to the problems and the many reviews that have taken place has merely emboldened shoddy builders, developers and tradespersons in the ACT," Mr Grant said.

"The defects exist because those responsible for its construction and assuring compliance with the ACT government's regulatory framework failed to deliver to the standards expected by the ACT community."

Mr Grant said Access Canberra needed to be more aggressive in enforcing standards and punishing substandard work.

"The regulator cannot be a friend of the industry, it must be prepared to enforce," he said.

"Access Canberra has to become a feared regulator. That doesn't mean it has to be overzealous, but it means that shoddy builders need to know that if they are building shoddy buildings then they will be in the gun."

Minister for Building Quality Improvement Gordon Ramsay did not respond directly to Mr Grant's comments, but defended Access Canberra's approach to regulation and enforcement.

The government has ramped up enforcement activity since the start of the year, including temporarily shutting down 32 building sites across Canberra.

"Each regulatory intervention by the regulator has an immediate impact on not only improving building quality through issues being rectified but also on hitting industry where it hurts - financially through mandatory rectification works and work stopping on sites," Mr Ramsay said.

"It also has an important reputational impact."

Morris Construction Corporation was contacted for comment.

The 100 submissions to the inquiry have laid bare the problems plaguing Canberra's construction sector, with numerous accounts of structural defects in buildings, delays in constructions and owners being left out of pocket after companies collapsed.

The role of private certifiers has also been called into questions amid concerns about the potential for conflicts of interest.

Mr Grant, who oversaw the introduction of private certification while leading the building codes board, said certifiers should be appointed by Access Canberra, not private builders.

A further five public hearings are scheduled for the inquiry between now and September.