The NSW premier has defended the right of owners of units in Sydney's beleaguered Opal Tower to sue the state government over their plight, saying she doesn't blame them for seeking compensation.

Law firm Corrs Chambers Westgarth confirmed it had lodged a class-action lawsuit against the Sydney Olympic Park Authority – the government body that owns the land on which the complex was built – in the NSW Supreme Court on Friday.

It’s unclear how many owners are involved, but the action is being led by owner Terry Williamson.

The newly-built block in Sydney Olympic Park was evacuated on Christmas Eve after cracks discovered in the building sparked fears it could collapse.

Premier Gladys Berejiklian said she didn’t know the details of the lawsuit.

“I don’t blame anybody for taking legal action to defend their own rights,” she told reporters on Tuesday.

“This is an unfortunate set of circumstances. We inherited the system we have today and we’re aiming to fix it by the end of the year through legislation.”

Ms Berejiklian said the government will be announcing a new building commissioner “imminently” to oversee the problem-plagued construction industry.

“(The commissioner) will ensure moving forward that everybody in the industry not only is aware of their responsibilities but delivers on those responsibilities to the nth degree,” she said.

In an update to residents in mid-July, the tower’s builder Icon said on site works have been “progressing well” and structural works should be completed by the end of the month.

Residents of 40 apartments in Opal Tower are set to be allowed to return to their units on Friday after inspections are carried out.

The body corporate’s engineers Cardno and BT Project management are attending the site regularly to inspect the structural works.

Source: AAP