Pro-Brexit group Leave.EU has today hired an adviser who has previously described the organisation as "mad", "useless" and producing "crap".
Dr Richard North, who has written numerous books critical of the EU, also accused Ukip leader Nigel Farage of talking “total, unmitigated bollocks” and making a “total prat” of himself after the Oldham West and Royton by-election.
Mr Farage is one of the key cheerleaders for the Leave.EU campaign.
In October, the Twitter feed linked to Dr North’s website, eureferendum.com, claimed Leave.EU was “run by a chimpanzee on drugs”.
Leave.eu today claimed Dr North was “one of the country’s foremost Eurosceptic thinkers” as they unveiled him as an adviser on their policy team.
Andy Wigmore, the group’s Head of Communications, described Dr North as being “hugely important in developing a Brexit strategy,” but in November Dr North publicly accused Mr Wigmore of making “basic errors” with the campaign.
Dr North has also taken aim at Arron Banks, one of the co-founders of Leave.EU, accusing him of “wasting his money” on the campaign, making “too many unforced mistakes poisoning the well…day on day.”
Mr Banks described the exchanges with Dr North, which took place on Twitter - as “very colourful discussions”, before praising him as one of the “Eurosceptic movement’s finest minds” who can help “present a clear, credible plan that will win people’s trust and expose the idle threats which make up the remain campaign’s Project Fear for what they are.”
In a statement on his website Dr North appeared to allude to the bickering as he wrote: "Following a meeting with Arron Banks and Andy Wigmore in Bristol last Tuesday, I have agreed to work with Leave.eu as a consultant for the duration of the EU Referendum campaign – unless, of course, we fall out and slaughter each other."
Dr North claimed Leave.EU has adopted his 'Flexcit' proposal as their formal exit plan.
This plan envisions the UK still having access to the single market, and therefore maintaining the freedom of movement rules which Ukip currently opposes.
Britain Stronger in Europe, the campaign urging for a 'remain' vote in the referendum, claimed 'Flexcit' would leave the UK paying money to Brussels without having any say over how it is spent.
Will Straw, Executive Director of Stronger In, said: "This would give the UK all of the costs but fundamentally undermine the benefits of EU membership, removing Britain's voice at the European top table. Britain would be forced into a position where it still has to pay, but has no say.
“Leave.EU have also openly attacked and abandoned UKIP’s central immigration policy, showing the utter chaos of the Leave campaigns. This is an extraordinary rejection of Nigel Farage’s most defining policy position."
Mr Wigmore claimed Stronger In were making a "gross misrepresentation of Flexcit" and added: “Far from having to “pay with no say”, countries like Norway and Iceland participate in hundreds of EU committees, helping to shape the Single Market regulations which they apply, retaining a veto where they find them particularly objectionable.
“Moreover, they have full control over their agricultural policies, external trade and fishing waters, unlike EU members.
“In any case, Flexcit sees the EEA as a stepping stone rather than a final destination.”