The warranty insurance covers homeowners against structural defects up to six years after a certificate of occupancy is issued and other defects for up to two years.

It also protects customers in the event their builder goes bust, dies or disappears before the project is completed.

Planning Minister, Mick Gentleman, has told Fairfax it is not the responsibility of private certifiers or the Constructions Occupations Registrar to verify the information provided to them for the issuing of commencement certificates and certificates of occupancy which are accepted as proof valid warranty insurance is in place.

Jerry Howard, the deputy executive director of the ACT Master Builders, disagrees saying "there is an expectation on the part of the consumer that the ACT Government regulator will do its job properly".

"The Constructions Occupations Registrar and the certifier (dealing with the project) need to cross reference the insurance certificate with the building contract," he said. "Under no circumstances should a commencement notice be issued unless the certifier and the regulator are absolutely convinced the build is covered by valid home warranty insurance."

Fairfax is aware of at least six former clients of failed builder Sublime Constructions who have been refused coverage under their home warranty insurance policies because QBE, the insurer, claimed the entity that took out the cover, Sublime Builders, was not the entity that actually built their homes.

"Accordingly your claim is denied as you are ineligible to claim due to the builder not being dead, disappeared or insolvent," QBE's Nick Nithiananthan wrote in a letter to one of the Sublime Constructions victims, Tanya Nguyen, in a letter dated August 15.

Mr Howard, Ms Nguyen and Thuy Ha, another homeowner caught out by the collapse of Sublime Constructions, say the Construction Occupations Registrar's refusal to accept any responsibility or to offer even a modicum of assistance and support to the Sublime Constructions victims highlighted "a massive chasm" between Environment and Sustainable Development's perception of its obligations to home builders and homebuyers and what the community expected.

They said it was remarkable that while the registrar removed Sublime Constructions and Development from the ESD list of licensed builders on April 2, 2014, it has not removed the company's nominated builder, Dee Sisomphou or two associated companies, Gantt Projects and Sublime Builders.

Mr Gentleman said Gantt Projects, which Fairfax understands was originally established my Sublime Constructions' Minh Phan and Dee Sisomphou but is now being operated by Mr Sisomphou alone, was licensed in the ACT in May 2013.

"The Gantt licence has not been active up until July 2014 (after the winding up of Sublime Constructions)," he said.

"The registrar is currently considering information with respect to that licence. Association of parties alone is not sufficient grounds for the registrar to not issue a licence."

Ms Nguyen, who noted the ACT Government issues the building licences, makes money off land sales and then collects fees from developers, builders, builder's clients and subsequent buyers, said it was appalling that when things went wrong the Environment and Planning Department's first response was to say "it's not our problem".

She first raised concerns about Sublime with the EPD on February 10 this year. EPD said the problem was "contractual in nature" and "not within the remit of the (construction occupations) registrar".

When Ms Nguyen took the issue to Fair Trading, as she had been advised, Fair Trading told her to go back to EPD.

Her next step was to go to the police and allege fraudulent activity. ACT Policing said her complaint would be difficult and time consuming to investigate.

It was suggested she take civil action against Sublime Constructions which is now in liquidation and, once the secured creditors are paid out, is unlikely to have any assets left to make good further claims.

The fraud squad has now "taken carriage" of her complaint and, after a lengthy delay, a case officer has finally been appointed.

Ms Nguyen was refused coverage by QBE after Sublime Constructions went into liquidation leaving her house partially completed even though a commencement certificate and a certificate of occupancy have both been issued.