UK Independence Party (UKIP) MP Douglas Carswell infiltrated the party to neutralise Nigel Farage, a new book from a former denier of the theory has claimed.

Carswell defected from the Conservatives in August 2014, claiming to be quitting his party in protest against David Cameron’s policies on a whole slate of issues, including European Union membership.

His motivations were almost immediately questioned by former UKIP staff members including the current Editor-in-Chief of Breitbart London, Raheem Kassam. At the time, Kassam accused Carswell and his close acquaintance Suzanne Evans of staging a “coup” against party leader Nigel Farage in May 2015.

But the theory was broadly ridiculed by the establishment media including Huffington Post journalist Owen Bennett, who is the author of a new book which confirms Kassam’s theories all along.

The “Brexit Club” book notes that Carswell’s move was part of a plot concocted with Tory Member of the European Parliament Daniel Hannan. They set out to fix what they termed the “Farage Paradox”, the Mail on Sunday has reported.

The pair are said to have met at the Tate Britain art gallery on the banks of the Thames to hold secret meetings on the matter.

“Angry, nativist Ukip risked being so toxic that if it ran the referendum it would do to the Eurosceptic cause what kryptonite did to Superman,” Carswell told Bennett, adding: “That could not be allowed to happen”.

Hannan said: “Douglas felt he could hold his seat under pretty much any colours and prevent Ukip losing us the referendum with a negative campaign.”

Carswell’s defection was lauded as a “political bombshell” at the time, not least as he chose to invoke a by-election in his Clacton seat under his new party banner.

At the time, he blamed a lack of seriousness on the European Union by Conservative Party leaders, among other policy matters: “The problem is that many of those at the top of the Conservative Party are simply not on our side. They aren’t serious about the change that Britain so desperately needs,” the Clacton MP told the BBC.

He added: “Of course they talk the talk before elections. They say what they feel they must say to get our support… but on so many issues – on modernising our politics, on the recall of MPs, on controlling our borders on less government, on bank reform, on cutting public debt, on an EU referendum – they never actually make it happen.”

And he said only UKIP could “shake up that cosy little clique called Westminster”.

His defection was welcomed by then UKIP leader Nigel Farage, who said: “What makes this even the more dramatic is that Douglas Carswell aims to test this with his constituency.

“Douglas has joined a growing political force that is not a pressure group and is picking up support across the political spectrum.”

Today, Mr. Farage took a different tone:

However, the pair soon fell out over the correct approach to take over immigration, and later backed different campaigns during the referendum on British membership of the EU, with Farage lending his weight to Leave.EU, while Carswell favoured the establishment Vote Leave campaign.

In August of this year, more than 2,000 UKIP members signed a petition calling on Carswell to resign from the Party, accusing him of “destroying the party by divide and rule” and “fighting against almost everything UKIP stands for”.

In the intervening period, Kassam set out to explain to Westminster establishment journalists that this was Mr. Carswell and Mr. Hannan’s plan all along. He was met by a chorus of derision, including from author Owen Bennett.

Speaking today, Kassam said: “I’m still waiting for the apologies, but at least now everyone knows what a fraud Douglas is”.