Last December the government asked the independent regulator IPART to investigate the pricing impact of the planned expansion and announced terms of reference for an investigation of costs and charges.

At the time water minister Melinda Pavey told IPART the government had asked the plant to prepare plans to expand its capacity to produce drinking water, saying this was a key element in protecting Sydney’s water security.

She said expansion of the Kurnell plant should be undertaken “as quickly as practicable to deliver an additional 250 megalitres of drinking water over 12 months”.