It is the ultimate case of political sour grapes.

New South Wales Premier Barry O’Farrell has announced his intention to resign as the state’s leader after the Independent Commission Against Corruption (ICAC) produced a handwritten thank you note for a gift in the form of a 1959 bottle of Penfolds Grange Hermitage that Mr O’Farrell had earlier denied receiving in evidence he gave to a probe by the watchdog into Australian Water Holdings (AWH).

During a press conference following his appearance as a witness at the ICAC hearing, the Mr O’Farrell emphatically denied – more than a dozen times – that he had ever received the upmarket bottle of plonk despite documentation from couriers that it had been delivered to his home in the North Shore suburb of Roseville.

At the press conference Mr O’Farrell then went on to say that it was a matter of civic duty for people called before the ICAC to appear and give truthful evidence, statements that subsequently went on to effectively destroy his chances of remaining in the job as Premier.

“I am absolutely delighted to be here because it sets an example for everyone else,” Mr O’Farrell told reporters yesterday.

“Part of my frustration as the Premier of this state is the fact that when it comes to shootings, people won’t come forward and cooperate with police. Part of my frustration with the way our justice system operates is too often witnesses won’t come forward,” Mr O’Farrell said.

“Well here today we have [a] demonstration that whether you’re a public servant, whether you are a private citizen, or the premier, if ICAC seeks your assistance it is your duty to attend to give honest evidence. That’s what I have done today. And if that sets an example for others, that’s a good thing for this state,” Mr O’Farrell said.

The 1959 bottle of wine, apparently picked on the basis that it was a vintage of the year that Mr O’Farrell was born, is alleged to have been sent by Nick Di Girolamo, a prominent fund raiser for the Liberal Party and an executive of AWH.

The ICAC is investigating whether there was corrupt conduct in relation to the activities of AWH executives and the company’s relationship to public utility Sydney Water as well as links to the family of corrupt former state NSW Labor Party powerbroker Eddie Obeid.

Ironically, Mr O’Farrell’s resignation is the second high-profile casualty for the Liberal Party stemming from ICAC’s investigation into AWH after highly respected federal Assistant Treasurer, Arthur Sinodinos stepped aside from his ministerial role in late March.

It has been reported by the ABC that Mr O’Farrell has already written to his parliamentary colleagues spelling out his intention to quit and explaining the circumstances under which he is doing so.

“This morning I was advised by the ICAC of a thank you note written by me for the bottle of wine. I still have no recollection of receiving the bottle of wine or writing the thank you note, but I accept the information presented to ICAC,” the Premier’s letter to MP’s, published by the ABC, said.

In the letter Mr O’Farrell said that he provided his “honest recollection of events and in no way attempted to mislead either the commission or public” and blamed the discrepancy on “what I can only describe as a what I can only describe as a massive failure of memory.”

“I’m proud of our achievements over the past three years, including getting underway infrastructure projects like the north-west rail links, north connection, west connection, signing up for the National Disability Insurance Scheme, the Gonski reforms and Murray-Darling Basin, and increasing numbers of teachers and police,” Mr O’Farrell wrote.

Mr O’Farrell said that he intended to continue to be “part of the Liberals and NSW parliamentary team.”

More to come.