Support for a no-deal Brexit has surged among grassroots Conservatives in fresh evidence of “blatant entryism” by former Ukip supporters, known as “Blukips”, as they prepare to pick Britain’s new prime minister.

No fewer than 77 per cent of members who joined after the 2017 general election back crashing out of the EU with no agreement, new research shows, in a further boost to Boris Johnson’s march to No 10.

The figure is far higher than the 60 per cent holding that opinion among pre-2015 members, offering proof of hardening views on Brexit just as rank-and-file Tories gain unprecedented power to decide Britain’s next leader.

For the first time, a prime minister will be chosen by party members alone, with Mr Johnson the overwhelming favourite after his vow to deliver Brexit by 31 October “deal or no deal”.

Arron Banks, Nigel Farage’s close ally, has boasted of encouraging hardline Brexiteers to join the Conservatives to influence policy – while also urging them to campaign for Mr Farage’s Brexit Party.

On Friday evening David Gauke, the justice secretary, saw off an attempt to deselect him, winning a vote of no confidence that had been called by activists in his South West Hertfordshire constituency.

Mr Gauke blamed “entryists” for the attempt to oust him, telling BBC Radio 4’s Today programme that “a fair number of those who joined the party in the last few months have not previously been party members”.

He added:: “It is the case that the person who organised the petition joined the party in February and the majority of those who organised a petition of 50 ... the majority of those 50 had joined in the last 12 months or so.

“Clearly there is a level of entryism but not sufficient, at least in my constituency, to cause me to lose such a vote.”

Meanwhile, Ken Clarke, the former chancellor, has become the latest senior Conservative to warn the party to highlight the “suspicious proportion of rather new members” with hardline views.

Farage launches his new Brexit Party: in pictures Show all 10 1 /10 Farage launches his new Brexit Party: in pictures Farage launches his new Brexit Party: in pictures Nigel Farage speaks at the launch of his new Brexit Party's campaign for the European elections Reuters Farage launches his new Brexit Party: in pictures Brexit Party candidate Annunziata Rees-Mogg, sister of Conservative MP Jacob Rees-Mogg, speaks at the launch AFP/Getty Farage launches his new Brexit Party: in pictures A supporter waits for Farage to speak AFP/Getty Farage launches his new Brexit Party: in pictures Supporters wait for Farage to speak AFP/Getty Farage launches his new Brexit Party: in pictures Farage's socks Reuters Farage launches his new Brexit Party: in pictures Farage and prospective candidate Annunziata Rees-Mogg wait at the launch AFP/Getty Farage launches his new Brexit Party: in pictures Supporters listen as Farage speaks AFP/Getty Farage launches his new Brexit Party: in pictures Free T-shirts for all attendees AFP/Getty Farage launches his new Brexit Party: in pictures Posters on the seats for supporters of the Brexit Party AFP/Getty Farage launches his new Brexit Party: in pictures A safety sign is pictured AFP/Getty

“They can’t possibly be Conservatives,” he told a Westminster event. “They should have joined the Brexit Party, or Ukip – probably some of them have in the past.”

Crucially, more than a third of the current membership joined after the 2016 Brexit referendum, according to a recent YouGov survey. The total has leapt to 160,000, from just 124,000 a year ago.

Now the research, carried out by Queen Mary University of London and the University of Sussex in a survey last month, has gained an insight into the make-up of those new recruits.

Back in the summer of 2015, two-thirds of members said they were undecided how to vote in the referendum announced for the following year, Tim Bale, the professor of politics at Queen Mary, said.

“Fast-forward to now and two-thirds of Tory members say they want not only Brexit and not only a hard Brexit (where we leave the customs union and the single market) but a no-deal Brexit,” he wrote in an article for The Independent.

Professor Bale said the survey could not confirm entryism, which he called “the idea that Brexiteers, and especially former Ukip members, should join the Conservative Party to influence its policies, its choice of candidates and its choice of leader”.

But, referring to the YouGov data, he pointed out: “What they do seem to show is that well over a third of the current Conservative Party membership joined after the 2016 referendum, which some will take as at least circumstantial evidence.

“What they also show is that, while no deal wins the support of ‘only’ 60 per cent of those members who had already joined the party by the 2015 election, that figure rises to 70 per cent for those who joined after the 2016 referendum, and to an astonishing 77 per cent of those who became Conservative Party members after the 2017 general election.”

“In short, attitudes on Europe have hardened among rank-and-file Tories,” Professor Bale added – describing that as “bloody good news for Boris Johnson”.

Former minister Sam Gyimah, who has faced attempts to deselect him over his opposition to Brexit, told The Independent: "From Militant in the 1980s to Momentum today, the lesson is clear: entryism is poison for democracies.

"We would be foolish to think the Conservatives are immune to it. This is about the drive for no deal and changing the very foundations of the party to turn it into an ideological sect."

Another Conservative MP said that Mr Banks was running a “hate campaign” and said they had witnessed entryism in their own constituency.

They said: “It is a concern. My impression is that the Conservative Party has changed substantially since the referendum. A lot of people who are moderates have given up – they’ve had enough and left. They’ve been replaced by less moderate people, and some are undoubtedly people who have voted Ukip in the past.”

They said the influx of new members had boosted Mr Johnson’s chances of becoming prime minister, adding: “In the long term, the Conservative Party ends up with a leader who is in the hands of the ERG [the European Research Group of hardline Eurosceptic]. With the views and the make-up of the membership as it is, we are turning into a party of the right – something that we’ve never been.”

Anna Soubry attacked “blatant entryism” when she quit the Tories for Change UK, adding: “It has been actively welcomed in some quarters. A purple momentum [Ukip’s colour] is subsuming the Conservative Party.”

Mr Gauke, who faced the no-confidence vote despite voting for Theresa May’s rejected deal three times, has previously highlighted how the activist pushing the motion backed the Brexit Party earlier this year.

Last month, Mr Banks boasted that his Leave.EU group recruited more than 25,000 new members to the Tories last year “to make the party Conservative again”.

He said many had joined to ensure they had a vote in the current leadership election and that their “collective power is felt by the candidates”.

In a tweet, Leave.EU had said it hoped to “claim our first cabinet scalp” by toppling Mr Gauke, adding: “With a new leader and potential election, now is the time to make the Conservative Party conservative again.

“If we fail? The Brexit Party wipes the floor with them. Win win!”

The research comes after Mr Johnson vowed to fire cabinet ministers opposed to a no-deal Brexit, a stance likely to trigger the departures of David Lidington, the de facto deputy prime minister, and Amber Rudd, the work and pensions secretary, as well as Mr Gauke.