Pro-EU Conservative MPs fear that a wave of UKIP members is trying to take over the party and oust Theresa May.

Two pro-Remain Tory "rebels" told Business Insider there has been a spike in the number of people joining their local Conservative branches, with most thought to be former UKIP supporters and hard Brexiteers.

However, they admitted that the party cannot block prospective members because they want a harder Brexit.

"We must accept that it is possible for a party to evolve and change as the views of its membership change," one leading pro-EU Conservative MP said.

Steven Woolfe, the former UKIP man who rejoined the Conservatives this week, told BI he wanted to "make the Conservative party conservative again" and kill any prospect of a soft Brexit.

LONDON — In recent months a battle has been raging in Conservative constituencies across Britain as Tory MPs fear they are being flooded by a wave of former UKIP members seeking to take control of their party.

Pro-EU MPs have reported a surge in new members since a call by the UKIP-donor Arron Banks for pro-Brexit activists to help overthrow Theresa May and force the hardest possible exit from the EU.

This summer has seen a battleground for these two rival brands of conservatism, with leading Conservative Remainer Anna Soubry already surviving a plot to oust her in her constituency of Broxtowe.

Leading pro-EU Tory MPs described to Business Insider two major influxes over the past few years: the first when David Cameron resigned and triggered a leadership contest; and the second over the last three months, with Brexit and May's position seemingly up for grabs.

They said their local memberships have increased by over 10% this summer. "People who went off the Tories in the early 90s, who look back at Thatcher with admiration and went to UKIP, are now coming back," one Conservative MP told BI.

The purple wave

Former UKIP MEP Steven Woolfe. Carl Court/Getty

One high profile member of the 'purple wave' flooding into the Conservative party is Steven Woolfe, the former UKIP MEP who re-joined the Conservative party this week.

He told BI that he had joined in order to "make the Conservative party conservative again," phase out the party's "pro-EU and social democratic" consensus, and bolster the fight to replace May's Chequers plan with a harder Brexit.

"I believe there is an opportunity for the Conservative party to reassess its own standing, and adopt some stronger core, conservative values," Woolfe said.

"It's now up to those on the Remain side like Anna Soubry and Sarah Wollaston to argue that their brand of Conservatism matches those who are joining the party.

"For us, they have got a long way to go. While people like Jacob Rees-Mo gg have more in common with ourselves."

'We can’t just exclude everyone'

Nigel Farage and Arron Banks in Bristol in October 2014. Matt Cardy/Getty

One concern among Conservative figures trying to push back against the wave of former UKIP members seeking to join is that the party headquarters doesn't have sufficient resources to identify members who have joined specifically to oust Prime Minister May.

"What the Conservative Party should be treating seriously is the coordinated attempt to flood the party with people whose intention it is to achieve a hard Brexit and/or get rid of the prime minister," one MP told BI.

"But it's very difficult. Occasionally you can identify new members as UKIP canvassers, but who are the others?"

Another Conservative MP said it had been difficult to check the backgrounds of new members, describing Conservative Campaign Headquarter's system for doing so as "outdated" and "absolutely s***."

They added: "We are almost certainly going to have a leadership contest in the next 12 months or so. £25 to pick the next prime minister is an absolute bargain."

We are almost certainly going to have a leadership contest in the next 12 months or so. £25 to pick the next prime minister is an absolute bargain.

But a bigger concern among the party's pro-EU "rebels" is that the Conservative membership is simply evolving, and moving closer to a more traditional, Jacob Rees-Mogg brand of conservatism — while leaving them behind.

"We can't complain that we don’t have enough members and then turn people away when they want to become members. We must embrace them. We can’t say no to Leave voters with conservative values," one pro-EU MP acknowledged.

This was echoed by a backbench colleague. "It’s not impossible for someone to support UKIP and then no longer agree with the direction of that party. We can’t just exclude everyone.

"We must accept that it is possible for a party to evolve and change as the views of its membership change."

One MP who BI spoke to about their enlarged local party membership described Arron Banks as a "disreputable individual" who is "bigoted in the extreme" but said they couldn't simply block all applicants who might share his political views.

Woolfe, who worked with Banks at UKIP, said the Tory party was now a natural home for the pair. "There are many people in the party who think I'm more Conservative than some Conservative MPs," he said.

A conference 'bloodbath'

The struggle for the soul of the party will be played out in Birmingham next month when the Conservative party meets up for its annual conference. Some pro-EU MPs told BI they are turning down invitations to partake in debates in order to avoid what is expected to be a "bloodbath" atmosphere.

Dominic Grieve, the pro-EU MP for Beaconsfield, revealed he won't be attending the conference for the first time in 25 years. However, he insisted this was because he would be abroad with the Intelligence and Security Committee.

One leading Europhile Conservative MP told BI they had rejected a series of invitations to appear on panels to avoid being "the Brexiteers' sacrificial lamb," saying the conference "is going to be a bit of a bloodbath."

They told BI that they expected the atmosphere to be "even worse" than the "horrible" conference in Manchester last year.

"At one Brexit event last year, when it came to questions from the floor, comments ranged from a prediction that MPs will be hanged from lampposts if they don't deliver Brexit, to a rant about what Muslims wear to the beach... And that was before any Brexit rebellion," they said.

Another Conservative MP told BI: "My firm intention is to avoid [conference] like the plague."