Former NSW premier Barry O'Farrell was one of three high-profile referees on John Barilaro's job application for a lucrative US trade role.
The former NSW deputy premier has told a parliamentary inquiry Mr O'Farrell had been a big supporter of his for more than a decade.
"He is a dear friend and I sent him a message and he offered to be my referee, it is as simple as that," he told the inquiry on Monday.
Controversy over Mr Barilaro's appointment to the coveted job has engulfed the Perrottet government since it was announced in June, claiming the scalp of minister Stuart Ayres after a draft review suggested he might have intervened in the hiring process.
Mr Barilaro also received a job reference from Department of Regional NSW secretary Gary Barnes and Ambassador to the United States Arthur Sinodinos.
Labor's Daniel Mookhey put to Mr Barilaro his prominent referees could have been "a key factor" in him getting the role.
Mr Barilaro rejected that.
"We have an apolitical public service personnel. What you are now questioning is their integrity," he said.
"I've been lucky enough to be surrounded by some very high-profile individuals ... I chose those referees based on that I believe they could sell me for who I was and what I'm capable of."
Mr Barilaro said his job applications often included "TBC" in the referee sections, and he would tailor recommendations for each job.
Mr O'Farrell, now Australia's high commissioner to India, resigned as NSW premier in 2014 after it was revealed he misled the Independent Commission Against Corruption, when he denied receiving a $3000 bottle of Grange Hermitage wine.
Mr Barilaro told the hearing Premier Dominic Perrottet also supported his bid for the role.
He flagged his interest in the job with the premier in November, one month after announcing his intention to resign from politics.
"He was just like, 'great', and that was it," Mr Barilaro said.
However, the former Nationals leader says he now regrets applying for the taxpayer-funded role, which he relinquished in June - two weeks after he was announced as the trade commissioner to the Americas.
"If I knew what I know now, I wouldn't have walked into what was a s**tshow," he said.
"Because the trauma I have gone through the last six, seven weeks has been significant."
No colleagues warned him applying for the job could cause political issues for the government, despite consulting Treasurer Matt Kean, Mr Ayres and the premier about his ambitions.
He strongly denied any wrongdoing and said many people had offered their support.
He agreed other candidates applying for the job would not have had the same access to the premier or ministers as he did, but rejected the suggestion that he created the role for himself.
Mr Barilaro's testimony about his interest in the role beginning in November conflicts with earlier evidence from his former chief of staff Mark Connell, who told the inquiry his former boss had his eye on the New York job soon after he became trade minister in 2019.
He also denied knowing public servant Jenny West had been selected as the successful candidate ten months before his appointment, saying a briefing document confirming her selection only contained his digital signature.
Mr Barilaro said he may have directed staff to sign the document for him.
Investment NSW chief executive Amy Brown will appear for a third time at the inquiry later on Monday.
NSW Labor has sought to expand the inquiry to look at other lucrative overseas-based roles and indicated it will abolish the positions if it wins government in March.
When asked about the recruitment process on Monday, the premier said he would implement recommendations from the independent review his government launched in June.
"It's clearly come to light there were issues in relation to the recruitment process," Mr Perrottet told 2GB radio.