New South Wales Energy Minister Chris Hartcher has resigned from the frontbench after the Independent Commission Against Corruption (ICAC) issued a search warrant against him.

The ICAC has been investigating the establishment of a trust fund to solicit donations for the Liberal Party.

It is claimed the trust company, which was set up by a staffer in Mr Hartcher's office, accepted donations from developers who are prohibited from contributing to political parties in NSW.

Mr Hartcher has issued a statement saying he is confident that he will be cleared of any wrongdoing.

He says he will continue as the member for Terrigal while he awaits the outcome of the ICAC investigation.

Several ICAC officials have been seen moving around inside Mr Hartcher's office at Erina on the state's central coast.

The ABC has sighted a notice on the front door saying the "office is temporarily closed" and apologising for any inconvenience. There has been no sign of Mr Hartcher.

The electorate offices of two factional colleagues on the central coast Darren Webber and Chris Spence have also been raided as part of the inquiry.

ICAC officials leave the office of former NSW energy minister Chris Hartcher ( ABC: Mary-Louise Vince )

State Premier Barry O'Farrell has issued a statement saying he spoke to Mr Hartcher earlier today from India.

"I accept and support Mr Hartcher's decision to resign from Cabinet following today's actions by ICAC," he said.

"Mr Hartcher advised me he is confident he will be cleared of any wrongdoing. However Chris said that, while the investigation is ongoing and in the interests of the Government, he feels it appropriate to resign from the ministry.

"I thank Mr Hartcher for his services to the Government and the state, in particular for his success in bringing electricity prices under control for NSW households and businesses after years of double-digit price rises under Labor."

Opposition Leader John Robertson says Mr O'Farrell's frontbench is starting to unravel.

"We have seen three senior ministers from the frontbench go in just four months," he said.

"Greg Pearce sacked by Barry O'Farrell, Graham Annesley resigned from the Parliament, and this morning after Chris Hartcher's office was raided by ICAC, he has also resigned.

"This Government is now more focused on its own internal workings and what's going on on the front bench than it is on dealing with the issues that are important to the people of NSW."

Mr Robertson says Mr Hartcher should be suspended from the Liberal party until allegations about illegal donations are cleared up.

Mr Robertson says all members are now under a cloud, referring to the raids on the electorate offices of two other central coast Liberal backbenchers in September.

"I've said the member for Wyong and the member for The Entrance should have been suspended from the Liberal Party," he said.

"I certainly think that Chris Hartcher should also be suspended from the Liberal Party while these investigations are on foot. Barry O'Farrell was elected promising something different, promising stability and certainty. Today yet again we've seen that promise collapse in a screaming heap."

NSW Premier forced into cabinet reshuffle

The Premier was forced to reshuffle his frontbench following the snap resignation.

Fair Trading Minister Anthony Roberts will be appointed Acting Minister for Resources and Energy, Special Minister of State and Minister for the Central Coast.

Mr O'Farrell says Stuart Ayres, the Member for Penrith, Parliamentary Secretary for Western Sydney and former Government Whip, will fill the vacant ministry position. Mr Ayres will be sworn in on Monday.

Greens MP John Kaye says Mr Hartcher had no option but to resign.

"Mr Hartcher has every right to be presumed to be innocent but he cannot continue as a minister as long as there is an ICAC investigation into himself and two of his close associates on the central coast," he said.

Greens mining spokesman Jeremy Buckingham has welcomed the resignation.

He has called on the Premier to appoint a minister who respects the importance of agriculture and water resources, and who will actively promote renewable energy.

"Minister Hartcher treated community concerns about mining with utter contempt and many people, including the Greens will be saying good riddance." he said.