Al-Qaeda chief Osama bin Laden's recently released video, in which he urged Americans to convert to Islam, has reportedly been branded as a 'fake' by his son in Britain.

According to 27-year-old Omar bin Laden's former British wife Jane Felix-Browne, her husband had told her, "that's not my dad."

"Omar is sure the man on the video is an imposter. He has seen it a few times and told me so twice," the 51-year-old granny told a British tabloid.

"Omar remembers the first video his dad did shortly after the 9/11 attacks. But he says in this latest one, Osama's beard is shorter and darker, his face isn't the same shape -- it's rounder -- and his eyes are clearly a different shape too.

"He doesn't think that his dad has had a make-over. He's sure it's not Osama," Felix-Browne said.

But she claimed that Omar, who has not seen his dad for eight years, "still believes he is alive and hopes to meet him one day."

"Osama may be the world's most wanted man, but Omar told me: 'I love my dad like any son and I miss him dreadfully'".

Felix-Browne, who had married Osama's fourth son last year, recently ended the relationship, fearing they would be killed by fanatics in Saudi Arabia because she is British.

"We got divorced on September 15. Ironically, it was also our first wedding anniversary. But the divorce was completely against our wishes," she had said recently.