Less than two weeks before the March 2015 poll, NSW Labor announced it was returning a $2200 donation from Santos after criticism from the Greens amid a fierce battle for the seat of Ballina.

Labor had announced that if elected it would permanently ban coal seam gas activity across the Northern Rivers. The Greens' candidate Tamara Smith went on to win the seat.

Data published by the Australian Electoral Commission reveals Santos donated $2000 to NSW Labor in January last year and $250 the following March.

"Once again Labor have been caught out taking easy money from a coal seam gas company, despite promising the public that they would not do so," said Greens MLC Jeremy Buckingham.

"Taking money from Santos shatters Labor's credibility when it comes to opposing coal seam gas.

"The public is tired of seeing Labor promise something in opposition and then do the bidding of their donors once they come to power. [Opposition leader] Luke Foley must return this dirty money."

A NSW Labor spokeswoman pointed out that the most recent donations were for federal election purposes.

"NSW Labor has accepted no donations from Santos for NSW state campaigns," she said.

In February it emerged that Santos has lodged an application to develop its controversial billion-dollar Narrabri coal seam gas project in and around the Pilliga Forest.

The Greens challenged Labor to state whether or not in power the party would tear up a production licence that might be issued by the Coalition government.

Opposition energy and resources spokesman Adam Searle said a Labor government would not do so – a position reflected in its bill promising a moratorium on coal seam gas activity.

"Any existing production lease in place will not be affected by Labor's moratorium," he said.

"That is why we are pressing for the bill to be passed in this Parliament and we call on all parties to support Labor's sensible and balanced legislation that resolves this important issue".