The U.K.'s Labour Party is urging an inquiry into the claim that some wealthy backers of Prime Minister Boris Johnson stand to profit if the U.K. leaves the EU without a deal on Oct. 31.

Phillip Hammond, the former Chancellor of the Exchequer from 2016 to 2019, said Saturday that wealthy supporters of Johnson have bet billions on a no-deal Brexit, and that these "radicals" who advise the prime minister "do not want a deal" with the European Union.

These claims prompted John McDonnell, the Labour Shadow Chancellor in the opposition, to write to Sir John Sidwell, Johnson's Cabinet Secretary, to launch a conflict of interest inquiry regarding Johnson's hedge fund supporters.

Johnson has been adamant that the U.K. leaves the EU at the deadline, with or without a deal.

Conservative business minister Nadim Zahawi, a supporter of Johnson, has said that Hammond's claims are "an ugly smear that is completely untrue."

Johnson has faced a series of setbacks and controversies in recent weeks.

On Friday, Johnson was referred to a police watchdog over his relationship to U.S. businesswoman Jennifer Arcuri while he was mayor of London and whether there was a conflict of interest.

Johnson, who was mayor from 2008 to 2016, gave Arcuri's firms two sponsorship grants from the mayor's promotional agency. She also was allowed to participate in several foreign trade missions despite not being eligible to do so.

Johnson's sister, Rachel Johnson, criticized his rhetoric when discussing Brexit, such as the use of the words "surrender" and "capitulation" when discussing the U.K.'s relationship with the EU.

Last Tuesday, the U.K.'s Supreme Court shot down Boris Johnson's plan to suspend the U.K.'s parliament for five weeks, with Labour leader Jeremy Corbyn calling on him to step down.