Chris Hartcher, the former Liberal state energy minister, and former NSW Labor treasurer Eric Roozendaal both fronted the Independent Commission Against Corruption on Tuesday to explain their relationship with Buildev, a property development company part-owned by Mr Tinkler.

In his second stint in the witness box, Mr Hartcher faced allegations his office had passed on cheques totalling $53,000 in illicit donations from Mr Tinkler to Liberal Party head office before the last election.

The money was allegedly "washed" through a Canberra front organisation called the Free Enterprise Foundation to disguise the fact the Liberals took the money in breach of NSW laws banning political donations from property developers.

"I'm not aware that they [the cheques] were sent from my office," Mr Hartcher told the inquiry. Asked if he denied that occurred, Mr Hartcher repeated: "I'm not aware of it."

The inquiry has heard the money was channelled back to the campaign coffers of former Newcastle Liberal MP Tim Owen and suspended Liberal MP Bart Bassett, who holds the western Sydney seat of Londonderry.

Mr Hartcher said an incriminating email from Mr Owen's campaign manager which said Mr Hartcher had sent a cheque to Liberal Party head office for the Newcastle campaign was a "puzzle" to him.

He also said he was not aware of whether Buildev fit the legal definition of a "prohibited donor" under electoral funding laws.

The former Liberal minister was asked about the identity of a mysterious "big man" referred to in a text message sent by Mr Owen's campaign manager Hugh Thomson to senior Liberal figure and former police minister Mike Gallacher.

ICAC has heard evidence that the text referred to an illegal $120,000 donation Mr Tinkler made to the Liberals' 2011 election campaign.

Mr Hartcher said that Mr Gallacher "always referred to [former premier] Barry O'Farrell as the big man" or the "big kahuna".

"That always used to amuse me, the big kahuna," Mr Hartcher added. "I don't know what kahuna means but I knew he was referring to the premier."

But Mr Hartcher cast doubt on claims by Mr Gallacher's lawyer that the "big man" text referred to Mr O'Farrell's attempts to secure funding from Liberal head office for seats in the Hunter.

"Did you ever have a conversation with anybody from the Liberal Party that suggested that Mr O'Farrell was behind money coming into the Hunter?" counsel assisting the inquiry, Geoffrey Watson, SC, asked.

"No," Mr Hartcher replied.

Mr Gallacher, who is also under investigation, is expected to give evidence later this week.

Mr Bassett, who started giving evidence on Tuesday, said he had no knowledge of illegal donations making their way into his campaign as all fund-raising was done at "arm's length" from him.

Mr Bassett's lawyer foreshadowed the MP may struggle to recall certain events because of health issues before the last election.

Mr Roozendaal faces allegations that he improperly took steps to benefit Buildev over its proposals for a coal loader in the Newcastle suburb of Mayfield.

Asked if he did "everything [he] could ... to support Buildev", he replied: "No."