Charles Perrottet, a sibling of ex-NSW premier Dominic Perrottet, was accused of tying himself in knots at the Independent Commission Against Corruption on Monday.
During an intense grilling, Mr Perrottet was forced to explain a 2021 message in which he appeared to ask developer Jean Nassif for a political donation.
Political donations from developers have been banned in NSW since 2009.
"Hi Jean, is there any chance I could drop over today to pick up that assistance for the upcoming pre-selections?" Mr Perrottet said in the message.
During a private hearing in June, Mr Perrottet told the commission he believed he was referring to picking up a statutory declaration from Nassif regarding political support from developers.
When asked about the message on Monday, Mr Perrottet claimed not to recall what it was referring to.
Counsel Assisting Peggy Dwyer showed Perrottet images taken from his phone the day after the message was sent of a cheque from Nassif for $148,000, made out to a consultancy firm Beckington.
Beckington was co-owned by close associates of Mr Perrottet's, Jeremy Greenwood and Christian Ellis, both of whom are also being investigated by the watchdog.
"The great truism about telling a lie Mr Perrottet is you have to be really good at remembering it," Dr Dwyer said.
"When you gave evidence in June this year you were picking up a stat dec, that was a lie, and when you gave evidence this morning you didn't know what you were picking up, that was a lie.
"And when you were confronted with the truth about it being a cheque, you're constructing your evidence around that - that's what's going on."
"Disagree," Mr Perrottet said.
Earlier on Monday, Mr Perrottet claimed he was lying to Nassif about helping him push plans through government channels in order to keep him onside.
"In politics sometimes you say things to people that aren't 100 per cent the truth," he said.
In a message to Nassif in early 2021, Mr Perrottet suggested he was assisting him in advancing planning approvals for three separate developments.
He claimed to have spoken to a contact in the Planning Delivery Unit, which operates to clear obstacles for stalled housing and developments.
Ms Dwyer suggested the message set out a detailed a clear plan to assist Nassif advance his developments.
But Mr Perrottet said he didn't actually have a contact in the unit and often made things up to tell Nassif to give him the view he was helping.
"He would have asked me for my help," he said.
"At times I would add my own political flavour to it to keep him on side ... ultimately, I made it up."
"Can I suggest to you, Mr Perrottet, you are tying yourself up in knots to try and keep things as vague as possible and to provide ludicrous explanations when different documents are shown," Ms Dwyer said.
"I am not," he replied.
Mr Perrottet fronted the commission briefly on Friday, admitting he met Nassif at least 10 times and that he may have told the developer he was working on getting rid of then-police minister David Elliott.
On the night his brother gained enough support to take over as premier from Gladys Berejiklian, Charles Perrottet sent a message to his wife allegedly regarding Mr Elliott.
"We execute they (sic) prick as soon as party room is over," it said.
Nassif, who is due to give evidence via video link later in the week, left Australia for his ancestral homeland of Lebanon in late 2022.
Mr Perrottet claimed the last time he communicated with Nassif was around that time.
A NSW police warrant has been issued for his arrest over fraud allegations, while his building empire Toplace collapsed into administration in mid-2023 while owing creditors billions of dollars.
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