The $344 million expansion of the Art Gallery of NSW is already delayed, with the state government still searching for a developer one year after it called for expressions of interest to build the project.

The Berejiklian government is evaluating bids from four parties to construct the Sydney Modern expansion, after it was forced back to the market amid a costings disagreement with construction giant Lendlease.

When the project was given planning approval in November, the Art Gallery released a statement saying construction would "commence in early 2019".

There are concerns over cost blowouts to the Sydney Modern project. Credit:SANAA

Lendlease last week submitted a new bid for the project. It was one of three companies shortlisted after expressions of interest were sought in August 2018. It is understood only Lendlease tendered for the project.