The billionaire businessman Donald Trump, star of the US version of The Apprentice and aspiring Republican presidential candidate, may have put the brakes on his campaign before it even got off the ground.

Interviewed on the Fox television network on Monday, Mr Trump appeared to throw in his lot with the "birthers" who question whether President Barack Obama was even born in the US, and therefore his right to hold the White House. Producing what he claimed was his own birth certificate, Mr Trump boasted: "It took me one hour to get my birth certificate. It's inconceivable that, after four years of questioning, the President still hasn't produced his birth certificate. I'm just asking President Obama to show the public his birth certificate. Why's he making an issue out of this?"

However, the stunt produced more questions than answers after it was revealed that the document could not, in fact, have been the proof Mr Trump had hoped would legitimise his own claims on the presidency.

Officials in New York said that all genuine birth certificates are issued with the Department of Health's seal, as well as the signature of the city registrar. Much to Mr Trump's embarrassment, his document carried neither.

Mr Obama was born in Hawaii in 1961, before moving with his mother to Indonesia five years later.