Brexit Party MEPs earn around four times more outside income on top of their EU salaries than representatives from any other party, figures show.

The findings, compiled by the NGO Transparency International, shows total side earnings from the party's 29-strong delegation is somewhere between €2,064,468 and €4,683,916 a year pre-tax.

The second biggest earning group is from the far-right Italian party League, which takes between €369,192 and €1,067,952 pre-tax.

Brexit Party MEP Benyamin Habib is the highest earning MEP in the entire parliament, taking in nearly a million euros – €960,000 – before tax.

He is paid the money by First Property Group, including a bonus averaging out at €80,000 a month.

Tory politician turned Brexit Party MEP Ann Widdecombe is also one of the legislatures highest earners – taking somewhere between €240,000 to €480,000 before tax.

She earns the money from broadcasting, speaking, and for her column at the Daily Express newspaper, where she is paid between €5,001 to €10,000 gross a month.

The party was criticised by other British MEPs, who said the Brexiteers were clearly part of the "elite" they railed against.

Labour MEP Julie Ward told The Independent: “The Brexit Party quite clearly treat being elected as an MEP as a part time role and are not interested in serving their constituents in the European Parliament. They are not a political party but rather a company, and these figures expose that. While railing against the 'elite” they are actually part of the 1%.”

Lib Dem MEP Martin Harwood said: "The fact that five of the top earners in the European Parliament are from the UK’s Brexit Party rather undermines their image as ordinary people taking on the fat cats in Brussels. They are some of the fattest cats in town! And clearly don’t have much to fear from the catastrophic Brexit they would impose on the rest of us."

Brexit Party MEP Ann Widdecombe is one of the highest earners (EbS)

All the earnings are on top of the MEPs' €8,757.70 a month EU salaries. MEPs also get an old-age pension from the age of 63, equal to 3.5 per cent of the salary earned from each full year served, up to a maximum of 70 per cent of the total salary.

Nick Aiossa, Head of EU Advocacy at Transparency International EU, said the figures showed it was crucial that the European Parliament establish a regulator to better scrutinise MEPs' interests.

“Given the number of outside activities declared and the sums of money involved, it is essential that an EU independent ethics body is established as a priority to weed out potential conflicts of interest," he said.

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"It must be ensured that this ethics body is well-resourced, can initiate investigations, give binding recommendations, and issue sanctions.”

A Brexit Party spokesperson defended his party's MEPs' outside earnings and said the figures showed they were good MEPs.

"Brexit Party MEPs were successful in real world before entering politics. They are real success stories in the outside world, entering public service should be applauded," he said.