The US president said three times that he agreed fully with "Jeffrey" during his presentation on G8 host Britain's plans to crack down on tax avoidance, leaving Osborne red-faced.
Realising his blunder afterwards, Obama joked that he had mistaken Britain's chancellor for the US soul singer Jeffrey Osborne, The Sun and the Financial Times reported.
"I'm sorry, man. I must have confused you with my favourite R and B singer," Obama was quoted as saying.
The chancellor, 42, bears little resemblance to Jeffrey Osborne, a 65-year-old African-American hit singer-songwriter known for his 1982 classic "On the Wings of Love".
Jeffrey Osborne told Sky News television: "I was really delighted actually. I was really not aware that (Obama) was that much of a fan that he would call the chancellor Jeffrey Osborne.
The Sun quoted an onlooker at the session as saying: "Osborne looked really put out" by what was a "visually crushing blow".
"The first time Obama did it was bad enough, but then he kept on repeating the error throughout the presentation. It got really cringe-worthy by the end."
George Osborne's real first name is Gideon, but he switched to George after being teased as a teenager.
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