The ''little white lie'' was his claim he knew virtually nothing about infrastructure company Australian Water Holdings, in which his family are alleged to have been ''secret stakeholders''.

The Independent Commission Against Corruption is investigating claims that Mr Obeid's father, former Labor minister Eddie Obeid, corruptly lobbied Labor colleagues on behalf of the company.

The inquiry has heard that Moses Obeid boasted the family could make $100 million out of a deal with the state government.

''What do you know about Australian Water Holdings?'' asked counsel assisting, Geoffrey Watson, SC, during a private examination of Mr Obeid last year. ''Nothing really,'' replied Mr Obeid.

''All right. Well, I think we're finished. Just pulling your leg, Mr Obeid,'' joked Mr Watson.

In the witness box on Wednesday, Mr Obeid maintained he knew nothing and also that his family did not have a shareholding in AWH.

He even tried to channel a former American president's famous denial when he said: ''I can put that to you in a Bill Clinton fashion: we did not have investor relations in that company.''

''Was Mr Clinton telling the truth?'' retorted Mr Watson, to the applause of the public gallery.

Mr Watson produced a heads of agreement which Mr Obeid had signed in November 2010.

It related to Obeid family friend Nick Di Girolamo selling the family a 30 per cent stakeholding in Australian Water for $3 million.

Mr Obeid claimed he had thought it was a loan and he hadn't noticed a heading which read ''Sale of shares''. ''I had a quick look at it, I signed the document, and I relied on my brothers that the rest of the things would be honky [sic] dory, so to speak,'' he said.

''Look, if it was untrue, Mr Watson, it was a little white lie.''

When Mr Watson suggested that his evidence was not to be believed, Mr Obeid shot back: ''That wouldn't be the first time.''

This was a reference to Mr Obeid's evidence at a previous inquiry resulting in a referral to the state prosecutor for potential criminal charges for perjury.

Counsel for Eddie Obeid, Stuart Littlemore, SC, objected when Mr Watson used the word ''old man'' when putting questions to Moses Obeid's older brother Paul.

Paul Obeid said his father was ''not happy'' about the $3.5 million the family has ''loaned'' AWH.

Also on Wednesday, the inquiry heard that Tim Koelma, an adviser to former NSW Liberal mining minister Chris Hartcher, went to work with Mr Di Girolamo soon after he left Mr Hartcher's office amid a political donations scandal.

Stacey Pittendrigh, a former personal assistant to Mr Di Girolamo, said both men worked at Anconna Resources in Bligh Street, along with Obeid family lawyer Sevag Chalabian.

She said she believed Anconna was ''to do with mining'' and Mr Di Girolamo was lobbying the O'Farrell government for the billion-dollar Wallarah 2 mine north of Wyong through his lobbying business Western Strategic Consulting.

Asked if Mr Koelma was researching ''material for Mr Di Girolamo to use for his lobbying'', she said: ''I believe so, yeah.''

ICAC is examining allegations that Mr Di Girolamo arranged for AWH to make ''regular payments'' to Eightbyfive, a company set up by Mr Koelma, in exchange for favourable treatment by Mr Hartcher.