Former New York City mayor Michael Bloomberg is considering a run as an independent candidate in the upcoming presidential election.

It is understood the billionaire businessman, who holds both conservative and liberal views, has told advisers he is willing to spend up to $1 billion (£700m) if he chooses to run.

He is said to be alarmed at the Democratic poll-leader Hillary Clinton’s alleged shift to the left and Republican frontrunner Donald Trump’s aggressive rhetoric on immigration.

If he did enter the race, Mr Bloomberg would be the second Jew - alongside Democratic candidate Bernie Sanders - to seek the presidency in November.

The Boston-born politician battled for the rights of Jewish communities and was applauded by Israel advocacy groups across the globe during his three-term, 12-year stretch as mayor.

Edward Rendell, a close ally of Mrs Clinton and a friend of Mr Bloomberg, told the New York Times that the likelihood of a run by the former mayor “rests on the not-impossible but somewhat unlikely circumstance of either Donald Trump or Ted Cruz versus Bernie Sanders.

“If Hillary wins the nomination, Hillary is mainstream enough that Mike would have no chance, and Mike’s not going to go on a suicide mission.”

An independent or third-party candidate has never won a US presidential election, with the most recent attempt in 1996 by another billionaire businessman, Ross Perot, earning him eight per cent of the vote.