The program was wound up in November 2022 after it emerged plastics consumers had returned to supermarkets to be recycled were instead put into storage.

The retailers involved say they had no knowledge of what was really happening but have since found stockpiles at 44 sites in six states around Australia.

There are 19 sites in NSW, 15 in Victoria, six in South Australia, two in Tasmania, one in Queensland and one in Western Australia.

Coles and Woolworths gained control of the stockpiles in late February and have contacted the operators of all 44 sites to make sure the plastic is being stored safely.

The supermarket giants are searching for an alternative recycling scheme but have warned it could be a slow process and are looking into shipping waste overseas to free up limited domestic recycling capacity.

"We're assessing logistics and warehousing arrangements for each stockpile on a case-by-case basis, as we continue to discuss recycling options with several reputable processors overseas," the companies said in a statement.

REDcycle previously said it was holding onto the waste while trying to ride out problems including the lack of recycling capacity.

The private company behind it has been placed in liquidation.

Australian Associated Press