Irishman Oisin Tymon – who spent six months off work on full pay – stunned BBC chiefs by turning down the offer, even though new host Evans personally gave it the go-ahead.
Instead, the 36-year-old launched a lawsuit against 55-year-old presenter for racial harassment and personal injury, and is seeking at least £100,000 damages from Clarkson and the Beeb.
His decision to sue has left BBC chiefs stunned – and presents a huge headache for Clarkson, who is desperate to settle the case.
A source close to the case revealed: “BBC executives feel a little disappointed that it has come to this – they have always been very supportive of Oisin and sympathetic to him.
“He had indicated that all he wanted to do was move on and go back to working on the show he loved – Top Gear.
“The BBC kept on paying him for six months after the incident in March until he was offered work on another show.
“However, after Chris Evans was confirmed as the new Top Gear host , he was asked if he would be happy to have Oisin back working on the show.
“Chris said he had heard good things about Oisin and that he was happy to work with such a good professional.
“Everyone thought that was it – until this racial harassment case emerged. It all seems very strange.”
Clarkson, who has signed a £160m to make a new show for Amazon Prime, has been keen to quietly settle the case – but BBC executives have refused to.
A source said: “Being sued for racial harassment is the last thing Jeremy needs right now – the Americans who he now works for have a zero tolerance for that kind of thing.”
Clarkson’s contracted with Top Gear wasn’t renewed by BBC chiefs after a big internal inquiry into what became known as the “Steakgate fracas”.
He was alleged to have struck Oisin – cutting his lip – and called him a “lazy Irish ****” in a bust-up over the lack of hot food in a north Yorkshire hotel after a long day’s filming.
After the incident Oisin went into hiding after receiving death threats from online trolls blaming him for Clarkson’s exit from the popular BBC 2 motoring show.
Clarkson also appealed to fans to stop trolling the producer, saying: “ All I would like to say is I wish people would leave Oisin alone, because none of this is his fault.”
Oisin has not spoken publicly, but after Clarkson’s contract was cancelled his lawyer said: “Through absolutely no fault of his own he found himself at the centre of a massive news story, but despite that he has conducted himself with dignity, restraint and balance.
“He now simply wishes to return to the job he loves at the BBC.”
Top Gear is due to return with Evans and a new line-up next May – while Clarkson, James May and Richard Hammond’s new Amazon Prime show is due to be screened late next year or early 2017.
Neither Oisin’s lawyers, the BBC or Clarkson had any comment to make.