Mr Sharp said he believed his selection process was conducted “by the book” following claims that he helped the then-prime minister secure a loan of up to £800,000.
The chair has been facing calls to stand down after it emerged that in late 2020 he had introduced billionaire Sam Blyth to cabinet secretary Simon Case to discuss whether the billionaire could act as a guarantor for the credit line.
But Mr Sharp insisted he would remain in place and was “confident” he had been given the job on merit rather than any favouritism in an interview with the BBC on Tuesday.
On Monday, public appointments commissioner William Shawcross announced he is to investigate Mr Sharp’s appointment as BBC chair in February 2021 to ensure it was done “fairly” and “on merit”.
Asked if he should stand down while the investigation is carried out, Mr Sharp said: “No, I’m confident that he will determine that I was appointed on merit. That’s obviously for him to conduct that investigation and process.”
Mr Sharp said he had contacted the cabinet secretary to discuss an offer of financial assistance from an “old friend” being made for Mr Johnson, before withdrawing from any further discussions.
“I had clarified and agreed with the cabinet secretary, both of us had the judgement that I’d avoided a conflict or a perception of conflict,” he said.
Mr Sharp confirmed that he dined with Mr Blyth and Mr Johnson at the then-prime minister’s country retreat Chequers in May 2021, after he had been confirmed as the government’s choice for the BBC role.
Asked how that meeting came about, he said: “Sam came to me and said, ‘Do you want to come to Chequers? I’m going down to have dinner with Al’ [short for Mr Johnson’s first name Alexander].
“I said, ‘Yeah, great’ – I’d never been to Chequers and Sam drove me down and we had dinner and I took advantage of that opportunity to bat for the BBC.”
The BBC chair also said the loan arrangement did not come up during the dinner at the prime minister’s grace-and-favour estate.
The former prime minister, who was responsible for Mr Sharp’s appointment, has dismissed the furore as a “load of complete nonsense” – saying he was “ding-dang sure” that Mr Sharp had no knowledge of his personal finances.
That point was echoed by the BBC chair, who said: “I don’t know anything about Boris Johnson’s finances” as that was “between him and his family”.
Mr Sharp was in the process of applying for the BBC chairmanship when he introduced Mr Blyth to Mr Case and was subsequently appointed to the role at the corporation.
Rishi Sunak, under pressure over Tory Party chair Nadhim Zahawi’s tax affairs, has sought to distance himself from the controversy, saying Mr Sharp’s appointment was made by “one of my predecessors”.