President Barack Obama has been highly critical of David Cameron over the Prime Minister's handling of foreign affairs.
The US leader said Libya had been left in a "mess" after the 2011 invasion because Mr Cameron had been "distracted by a range of other things".
In an interview with The Atlantic magazine, Mr Obama said: "When I go back and I ask myself what went wrong, there's room for criticism, because I had more faith in the Europeans, given Libya's proximity, being invested in the follow-up."
It is rare for a serving President to so publicly attack a serving British Prime Minister, although few would argue with his assessment.
The US President also noted the French president at the time, Nicolas Sarkozy, lost his job the year after the 2011 invasion and criticised the French eagerness to take credit for overthrowing Colonel Muammar Gaddafi.
Mr Obama said: "Sarkozy wanted to trumpet the flights he was taking in the air campaign, despite the fact that we had wiped out all the air defences and essentially set up the entire infrastructure."
Mr Cameron and Mr Sarkozy paid an infamous visit to Libya in September 2011 to be greeted as heroes and liberators.
Five years later, Islamic State is taking hold in the east of the country, no government has been formed, and Washington is considering a new intervention.
In the lengthy interview, that runs to 72 pages, President Obama also said that "free riders aggravate me," in a pointed barb at Britain's reluctance to spend 2% of GDP on the armed forces.
"You have to pay your fair share" he told Mr Cameron and said Britain would no longer be able to claim a "special relationship" if it didn't.