The Independent Commission Against Corruption (ICAC) formally asked for the right to use the recordings as part of its probe into the alleged stacking of a Sydney council in order to influence planning decisions.
Attorney-General Michael Daley this week granted the ICAC request to allow it to use the material, with the provision to automatically expire at the end of 2025.
Earlier in the month, ICAC chief commissioner John Hatzistergos informed the government the anti-corruption agency had obtained "certain evidence which appears to be records of private conversations made by a third-party".
Mr Hatzistergos said while the recordings were of interest to its investigation, they might have been made in breach of surveillance laws.
The NSW regulations ban the recording of private conversations without the consent of all the main parties involved.
The ICAC investigation stems from allegations made by state Liberal MP Ray Williams last year under parliamentary privilege.
He said senior party members were paid to install councillors on The Hills Shire Council who would support development applications from Nassif's company, Toplace.
Police recently issued a warrant for Nassif's arrest amid allegations a $150 million loan from Westpac was obtained using fraudulent pre-sale documents for an apartment complex in Castle Hill.
The 55-year-old left the country on December 22 and his exact whereabouts are unknown, although he is reported to be living in rural Lebanon.
Since his departure, Toplace has been placed into administration as it deals with a series of defect notices for multiple apartment blocks.
Last month, Premier Chris Minns urged Nassif to turn himself in to authorities following news of the company's financial strife.
"I would encourage him (Nassif) to make himself available to investigators in NSW so that we can find out exactly what he's done in this state and what his potential liabilities are," he said.
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