Owners and residents of Sydney's Mascot Towers have been advised existing cracks in the building have widened and new cracking has developed requiring urgent remediation works to avoid a "structural failure".

Key points: A new report from the law firm representing owners has found the condition of the building is worsening

A new report from the law firm representing owners has found the condition of the building is worsening Mascot Towers was evacuated in June after serious structural issues were discovered

Mascot Towers was evacuated in June after serious structural issues were discovered One apartment owner said the building was a "catastrophic failure"

In the latest update on the troubled apartment block, law firm Mills Oakley, acting on behalf of the owners corporation, said engineers had found cracking around the north-eastern transfer beams and the basement was of "significant concern".

The report also suggests waterproofing systems used to excavate the basement levels of the new neighbouring Peak Towers construction "likely caused the erosion of fine particles and the destabilisation of land supporting Mascot Towers".

Apartment owner Brian Tucker said it was another blow on top of huge levies owners were already being asked to pay, and called on the State Government to provide more financial support through a low-interest loan.

"It's absolutely devastating. From what I believe the latest information is the building is a catastrophic failure," Mr Tucker said.

"And the problem is that, as an owners corporation, we need to fund this building for building stabilisation.

"And we don't have the money to do that."

Mascot Towers residents were evacuated in June after cracks were discovered in the building. ( AAP: Bianca De Marchi )

Mr Tucker, who is also a engineering lecturer at the University of NSW, said he believed the building was still moving.

"It's going to be a long, drawn out process, maybe four or five years," he said.

"We need this money immediately to try and stop this building collapsing as per the engineers' report.

"My partner and I have paid this levy this week which is $13,000 and at the end of the month we're up for another $10,000. We just can't afford this."

The developer of the Peak Towers building, ALAND, has previously rejected speculation the development was linked to the cracks.

A spokesperson for the Owners Corporation said engineers were "confident" the cracking did not indicate the building was unsafe.

"But it could get to that point if immediate steps aren't taken to improve the bearing capacity of the soil supporting the slab," the spokesperson said.

The building will be closed to owners on Thursday so remediation works can begin.