But Green groups, including the Australian Conservation Foundation, have described the pledge as “lame and inadequate”.

The ABC current affairs program on Monday aired leaked recordings of Mr Hanlon – now a top NSW water bureaucrat – apparently offering to share confidential information with irrigation lobbyists, including a possible plan to withdraw the state from the Murray Darling Basin Plan altogether.

Mr Hanlon held the top job at Coliban between 2008 and 2011 before he was appointed managing director of Goulburn-Murray Water.

On Tuesday, Niall Blair, the NSW primary industries minister, said he had "asked for a clarification around the circumstances" of the briefing given by Mr Hanlon, in the head of the department's water division.

"I have directed the Secretary of the NSW Department of Industry to provide an urgent overview of all the compliance matters raised in the program," Mr Blair said in a media statement.

The Four Corners report raised other issues including the apparent gutting of a Strategic Investigations Unit set up in the wake of previous reviews by the state's Ombudsman to strengthen compliance of water restrictions.

The unit identified several cases by large cotton farming combines that indicated billions of litres of water had been diverted into huge dams at periods of low river flow even when major downstream centres such as Broken Hill were at risk of running dry.

Mr Blair said his department's secretary would seek advice from Ombudsman to "maximise the effectiveness of the investigation" into regulation implementation launched a year ago.

"The NSW Government remains committed to the Murray Darling Basin Plan, while seeking the best deal for NSW communities within that framework," he said, referring to claims by Mr Hanlon caught on tape that there was a "Plan B" to pull the state out of the plan.

​"We have had detailed legal advice on what walking away means," Mr Hanlon told the group described by the ABC as made up by irrigators and their lobbyists.

"Before we walk away we would dare them to step in over the top of what we're doing if we're acting in good faith, delivering on what we should, and they start carrying on, we would say we dare you to bloody step in over the top of us," Mr Hanlon is heard to say, offering a one-page legal summary.

He is also heard offering to supply information to support the lobbyists' cause as "ammunition" but stripped of the department's logo to conceal its source.

Paul Sinclair, campaign director of the Australian Conservation Foundation, said Mr Blair's response was "lame and inadequate".

His organisation would be contacting the state's Independent Commission Against Corruption to begin  an investigation into the allegations and for a Senate inquiry to probe the effective diversion of a large share of the billions of dollars spent on improving the health of the river amid excess water extraction across the basin.

"Instead of saving the river, it looks like the Murray-Darling Basin Plan has made a fortune for a lucky few. The government has to step in to fix abuses now if we are going to save our most precious water system," Mr Sinclair said.

Kate Smolski, chief executive of the NSW Nature Conservation Council, called on Premier Gladys Berejikilian to remove National Party MPs from natural resources portfolios and refer the issues raised to ICAC.

"The government has turned a blind eye to illegal behaviour like meter tampering water theft," Ms Smolski said. "This scandal has happened on the watch of National Party ministers who must be held to account for their mismanagement of one of the key natural resource agencies in NSW.

Fairfax Media has sought to speak to Mr Hanlon.

According to the media release announcing his appointment on December 9, 2014, Mr Hanlon joined the government from the Goulburn Murray Water where he had been managing director.