Tom Hayes, 44, a former Citigroup and UBS trader, was handed a 14-year jail sentence - cut to 11 years on appeal - in 2015, which was one of the toughest ever to be imposed for white-collar crime in UK history.

His case, as well as that of Carlo Palombo, 45, who was jailed for four years in 2019 over rigging the Euribor interest rates, was referred to the Court of Appeal by the Criminal Cases Review Commission (CCRC), which investigates potential miscarriages of justice.

Their lawyers told judges they should follow the approach of a US appeals court which in January 2022 overturned the convictions of two former Deutsche Bank traders' convictions for Libor rigging.

The Serious Fraud Office (SFO) opposed the appeals saying they "reveal no new reason for questioning the approach and findings of this court on several prior occasions".

Three judges today dismissed the appeals and Hayes and Palombo were given 14 days to apply for permission to appeal to the Supreme Court.

Outside court, Hayes described the decision as a "shock" and said he would be taking his case to the UK's highest court, adding: "I'm a fighter, not a quitter. We haven't given up."

Hayes, a gifted mathematician who is autistic, was described at his Southwark Crown Court trial as the "ringmaster" at the centre of an enormous fraud to manipulate benchmark interest rates and boost his own six-figure earnings.

He was found guilty of multiple counts of conspiracy to defraud by manipulating Libor - a benchmark rate once used to price trillions of financial products globally - between 2006 and 2010 and spent five and a half years in prison before he was released on licence in 2021.

Hayes has always maintained that the Libor rates he requested fell within a permissible range and that
his conduct was common at the time and condoned by bosses.

He was one of 19 people prosecuted for trader manipulation and one of nine convicted - all of whom have since brought unsuccessful appeal bids, according to the SFO.

Palombo, an ex-vice president of euro rates at Barclays bank, was found guilty of conspiring with others to submit false or misleading Euribor - the euro equivalent of Libor - submissions between 2005 and 2009.

He previously lost a bid to overturn his conviction at the Court of Appeal in December 2020, while Hayes failed to overturn his conviction in December 2015, when his sentence was cut by three years.

An SFO spokesperson said: "The Court of Appeal's judgment is clear that these convictions for fraud are still as relevant today as 10 years ago.

"No one is above the law and the court has recognised that these convictions stand firm."