One of Frank Sinatra’s closest friends has insisted the idea the late singer was Ronan Farrow’s real father is “absurd”.

Frank Sinatra and Mia Farrow

Frank Sinatra and Mia Farrow

The ‘My Way’ hitmaker’s ex-wife Mia Farrow – who he split from in 1968, more than 20 years before the birth of her son in December 1989 – previously suggested the legendary crooner could “possibly” be the journalist’s biological dad but Tony Oppedisano has insisted the theory is virtually impossible.

In extracts from his new memoir ‘Sinatra and Me: In the Wee Small Hours’, published by People magazine, he wrote: "There's been a lot of gossip about Frank's possibly being Ronan's biological father. Rumours I believe I'm a position to tamp down."

Tony explained how the former couple stayed friends long after their two-year marriage ended and he even arranged for a secret meet-up between the pair at the Waldorf Astoria hotel when Frank was staying there as Mia was going through a difficult time in her relationship with Woody Allen.

He recalled: “When she was beginning to have problems with Woody she was looking for some comfort and it was like two old friends catching up. She was devastated and he was there to support her."

Tony also insisted his pal’s health issues would have made it virtually impossible for him to be Ronan’s father as he "had to wear a colostomy bag until he fully recovered” from diverticulitis surgery in late 1986, and also cited the singer’s hectic schedule as another reason for the theory to be highly unlikely.

He wrote: “There are only two ways Frank could have fathered Ronan, both absurd.

“Either Mia made a secret trip to shack up with Frank in his California home with [fourth wife] Barbara present, or Frank, wearing his always romantic colostomy bag, made a quick trip to Connecticut between his Atlantic City performances."

And the writer insisted it would have been out of character for Frank to have ignored his responsibilities if he was Ronan’s father.

He said: “If Ronan had been Frank's son, Frank would have acknowledged him.”

After Mia claimed Frank could “possibly” have been her son’s dad in 2013, five years later her former partner Woody admitted he “wouldn’t bet [his] life” on being Ronan’s father.

He said: “In my opinion, he's my child. I think he is, but I wouldn't bet my life on it."

And Ronan himself has branded the claims “ridiculous”.

He has said: “I appreciate how hilarious it is. I mean, it's a ridiculous situation. That said, I'm pretty unfazed by it in substance, because it's been out there both publicly and privately for so long.

“You know, I have a relationship that I'm very happy with, you know, with all parties involved. For me, the imperative is 'all right, we've talked about it, I get a kick out of it, everyone gets a kick out of it."