Bookmakers Paddy Power lost $4.5million on Donald Trump's shock win after the firm paid out $1million to punters who backed Hillary Clinton - before the US election was over.

The controversial billionaire, 70, was the underdog in the two-horse race before the shock result was announced on Wednesday morning.

Irish firm Paddy Power was so confident that Clinton, 69, would be the 45th President that they even paid out to customers who backed her - in October.

Paddy Power lost a staggering $4.5million after it was announced Donald Trump would be the next President

But the company has been forced to cough up $4.5million - £3.6million - their 'biggest political payout' since it was set up in 1988.

A huge number of customers backed the former Apprentice star and his odds were dramatically slashed when the FBI announced they were investigating Clinton's private email server.

Trump had seen his initial odds of 100/1 - which were available from November 2012 to June 2015 - drop to 13/8 in May 2016.

On October 20, punters could have got 9/2 on Trump becoming the next President, and the odds represented an 18.2 per cent of winning.

The Irish firm was so confident that Clinton, 69, (pictured) would be the 45th President that they paid out to customers who backed her - in October

Just before the firm rewarded customers who backed Clinton, her odds had dropped to 2/11 - meaning she had an 84.6 per cent of winning, according to the bookmakers.

Féilim Mac An Iomaire, from Paddy Power, said: 'We're in the business of making predictions and decided to put our neck on the line by paying out early on Hillary Clinton, but boy did we get it wrong.