Barack Obama’s former chief of staff Rahm Emanuel has offered a charity reward if an internet user pretending to be him on Twitter comes forward.

The politician, who is in the last stages of his campaign to become the next mayor of Chicago, has offered up to £3,100 if the person reveals their identity.

The Twitter account, unlike Mr Emanuel’s real one, is filled with angry and often obscene remarks, in recognition of Mr Emanuel’s famously short temper.

“@MayorEmanuel” has 2,000 more followers on Twitter than Mr Emanuel.

Mr Emanuel, who served as aide to Bill Clinton during his presidency, said: "After the election, I am offering a donation to the charity of that gentleman or woman's choice.”

He added that the fake account had caused some confusion. He said: "A lot of people say, 'I just read your tweet,' and I say, 'Huh?'".

It is not the first time a fictional version of Mr Emanuel has caught public attention. Josh Lyman, deputy chief of staff in the White House of Aaron Sorkin’s West Wing, was said to be based on him.

Mr Emanuel is also not the first public figure to fall victim to a fake tweeter.

Last year Melanie Phillips was rumoured to have joined and even gained 800 followers before she blogged: “For anyone who may have been taken in by an impersonator who is pretending that I am now on Twitter, let me make it clear – I am not on Twitter and have never uttered a single Tweet.”