AGL's failure to make full and timely disclosures of its NSW political donations appears to extend to other projects beyond its Gloucester coal seam gas venture, including the proposed $300 million Tomago gas storage facility near Newcastle, documents show.

The energy giant was forced to concede disclosure errors on Thursday after a review by its external auditors Deloitte found the company had ''failed to fully comply'' with the Environmental Planning and Assessment (EP&A) Act.

Gloucester residents protesting against AGL. Credit:Newcastle Herald

''AGL is separately determining whether, and the extent to which, reporting obligations in relation to other planning applications made by AGL may not have been complied with,'' AGL said in a statement.

Among suspect projects is the Tomago plant, the destination for any CSG extracted from the Gloucester Gas Project.