A prominent Liberal Party fund-raiser and associate of the Obeid family "buttered up" NSW Premier Barry O'Farrell by sending him a $3000 bottle of Penfolds Grange, a corruption inquiry has heard.

Nick Di Girolamo, a key player in the Independent Commission Against Corruption's inquiry into Obeid-linked company Australian Water Holdings, said he had Mr O'Farrell's mobile number and would call him "once a month, once every couple of weeks".

In his second stint in the witness box, the former chief executive of Australian Water admitted on Tuesday that he sent Mr O'Farrell a bottle of Grange costing $2978 in April 2011, shortly after the Liberal Premier won the March election.