Reform UK has pledged to imprison the bosses of companies employing illegal migrants and said it would fine larger firms 10 per cent of their global revenues.

The party said its aim was to stop delivery and gig-economy companies from profiting from illegal workers "without consequences".

Home affairs spokesperson Zia Yusuf said, "young British people are being shut out of entry-level jobs and our whole economy is being undermined".

The Home Office said it was already increasing penalties for companies hiring illegal workers. A source within the department called some of Reform's proposals "empty posturing".

Reform said that if it won the next general election, it would pass a law making chief executives and directors of large companies profiting from illegal workers personally and criminally liable.

That would be regardless of their knowledge of workers' legal status.

The party said this would be similar to the personal liability of senior managers for the financial misconduct of their firms under Financial Conduct Authority rules.

Reform would also introduce a phone line for the public to report suspected illegal working or organised criminal activity, which police and other authorities, such as trading standards teams, would be required to follow up.

Reports resulting in successful prosecutions would be rewarded with a share of any fines generated.

Yusuf said the party "would introduce the toughest penalties anywhere in the world for illegal working".

Fines are already being imposed on organisations found to be in breach of immigration laws, with one council fined £45,000 for employing one illegal worker in June.

A Home Office source said of Reform's announcement: "The Government is already doing much of this. The rest is just empty posturing."

A spokesperson for the department added: "We are already closing the loopholes that allow illegal migrants to work in the UK by extending right to work checks to the gig economy and delivery sector.

"Employers who break the law face severe consequences, including fines of up to £60,000 per illegal worker, business closures, licence revocations and prison sentences of up to five years."

They added that since Labour came to power, Immigration Enforcement action has increased "to the highest level in British history, with illegal working arrests up by 83% and raids up by 77%."