Mr O’Farrell stood down on Wednesday morning after a handwritten thank-you note emerged, proving that he had received a $3000 bottle of wine from a businessman linked with the Obeid family.

Mr Carr was at Dymocks in Brisbane city to sign copies of his controversial new book, Diary of a Foreign Minister, and refused to say whether Mr O’Farrell’s “significant memory fail” about the 1959 Grange wine was plausible.

“Given that the premier’s resigned, I don’t think there’s any more in argument, the point is he’s accepted the case and that’s really all that matters at this point,” he said.

Mr Carr said resignation was Mr O’Farrell’s only real choice.

“Fundamentally yes ... as the evidence was emerging I think even his closest friends and supporters would say there was going to be no alternative to this,” he said.

“He’s made what is a tough decision for anyone in leadership and I just wish him and his wife all the best for what lies ahead of them.’’

Mr Carr rejected the suggestion that it was ironic that ICAC’s biggest scalp has been a Liberal premier, when it had been a millstone around the Labor Party’s neck.

“If you’re in politics in New South Wales, you’ve got to appreciate that the ICAC is sitting there ready to judge your behaviour, backed by a very strong piece of law,” he said.

“The goal of any premier should be to see that standards are enforced through his government, and that he or she is not suffering a loss from an ICAC inquiry.”

Mr Carr has attracted criticism about the parts of his diary that focus on diet and exercise.

He said having given up drinking three years ago, he wouldn’t know how many calories were in a bottle of ’59 Grange.

“Too many ... wine is full of sugar, and after wasting too much of my life savouring good wine, I reached a decision that the disadvantages outweigh the joy of the stuff,” he said.

“As tempted as I am by a wonderful pinot noir from time to time, I think being clear-headed is the better course.”

Mr Carr said his book deserved to be judged as a whole, not just on the controversial parts already widely discussed in the media, such as his preference for first class travel and Hermes or Bulgari ties, and use of one-legged Romanian deadlifts to help develop ‘‘deep-cut obliques.’’

“There is no resemblance between what has been written about the book in many places, and the book itself,” he said.

“So there’s a delicious surprise awaiting those people who buy the book and actually open it.”

He said he planned to write more, but hadn’t yet settled on a topic.

“There’ll be no more diaries ... it’s hard work, and my life is far less interesting now anyway.”