The National Gallery of Australia has postponed a major exhibition of Aboriginal art, saying it needs more time to probe allegations of interference.

The Ngura Pulka Epic Country exhibition had been scheduled to run from June 3 until October 8.

The gallery has described it as “one of the largest and most significant First Nations community-driven art projects to have ever been developed”.

Artworks from the APY (Anangu Pitjantjatjara Yankunytjatjara) Lands were to have starred in the show.

But in April, The Australian newspaper published allegations non-Indigenous workers from APY Art Centre Collective had painted on works by Aboriginal artists.

The collective has “strenuously” denied the accusations, saying they are false and defamatory.

An independent review panel appointed by the NGA needs more time to fully complete the investigation, the gallery said in a statement on Wednesday.

Copyright lawyers Colin Golvan and Shane Simpson are running the review, assisted by first nations experts Yhonnie Scarce and Professor Maree Meredith.

They are examining whether the 28 paintings in the show were made under the creative control of the artists they are attributed to, and to what extent studio assistants and managers at the APY Art Centre Collective may have contributed.

The gallery has promised to publicly release their final report.

The NGA will also await the results of a second probe by the Australian, South Australian and Northern Territory governments announced in May but the terms of reference and time frame for the government review are yet to be decided.

Delaying the exhibition leaves the gallery in an even more difficult position: Ngura Pulka was a key part of its winter program and there’s still no word on what will replace it.

A gallery spokesperson said there was no timeline for when Ngura Pulka might go on show, as it cannot pre-empt the outcome of the reviews.

A statement released on Wednesday said “the National Gallery is committed to continuing to work with APY Lands artists and supporting their ground-breaking work”.

The decision to delay the exhibition was made by the NGA Council, the gallery said.