Barack Obama sent a damning email to ex-White House doctor, Ronny Jackson, ordering him to stop his "unprofessional behaviour" after he posted a "cheap shot" about US President Joe Biden's mental state, a book claims.
Republican Congressman Dr Jackson shared his view on Mr Biden's mental capacity in a series of tweets during the 2020 campaign season.
The Texas Republican took to Twitter, saying: "Biden was on TV again, making crazy statements and concerning mental gaffes.
"He didn't know what state he was in or what office he was campaigning for."
Barack Obama allegedly criticised Dr Jackson for his comments Jane Barlow
Criticising Mr Biden, he said: "He apparently thought at one point that he was running for the Senate and later couldn't remember what state he was campaigning in.
"This had been going on for months and was getting worse."
The former doctor to Mr Obama, George W Bush and Donald Trump claimed he was technically qualified to assess the health of the current White House resident.
Dr Jackson was also running for Congress in 2020 and tweeted about Mr Biden's cognitive "frailty".
He continued: "Remember the cognitive test that I gave @realDonaldTrump? The one he aced! Sounds like somebody else might need some testing done!! Scary!!"
His comments sparked fury from many Democrat voters and representatives, with Mr Obama allegedly retaliating to the doctor's claims in a passionate email.
Joe Biden announced his intentions to run for the 2024 presidential election KEVIN LAMARQUE
Writing in his new book, Dr Jackson claims he received a strongly-worded email from Mr Obama just 20 minutes after the tweet surfaced.
He claims Mr Obama highlighted how he had refrained from commenting on Dr Jackson's interaction with his successor, but praised him for his help with his family while he served as US President between 2009 to 2017.
Despite the upbeat and positive start to his email, the former US President is then said to have slammed the doctor for his comments.
He allegedly wrote: "I have to express my disappointment at the cheap shot you took at Joe Biden via Twitter.
"It was unprofessional and beneath the office that you once held.
"It was also disrespectful to me and the many friends you had in our administration.
"You were the personal physician to the President of the United States as well as an admiral in the US Navy.
"I expect better, and I hope upon reflection that you will expect more of yourself in the future."
The former White House doctor was a notable supporter of President Trump, describing him as being in "excellent" mental shape.
Dr Jackson's memoir, Holding the Line: A Lifetime of Defending Democracy, is due to be released on July 26. Its release has been reported by Fox News.