The Conservative party has become a “politically religious sect” under Boris Johnson with “Brexit as the one only god” and Dominic Cummings as its “archbishop” leading an “inquisition”, a top donor has said.

Alexander Temerko, who has given more than £1m to the Tories, told HuffPost UK it was “absolutely crucial” for the party to shift back towards the centre if it wanted to be successful.

He spoke as Boris Johnson told the cabinet he was “the most liberal Conservative PM in decades”, in an attempt to respond to criticism over his decision to purge 21 rebels who voted to block a no-deal Brexit.

Temerko said he agreed with one of the rebels, Philip Hammond, who has vowed to fight for his place in the Conservative party to “stop it becoming a nationalist party with a small, separated, isolated agenda”.

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Johnson insisted at cabinet that he was running a one nation government, as senior ministers set out pledges including the recruitment of 20,000 extra police officers, a £7.1bn boost for schools funding by 2022 and £33.9bn a year extra for the NHS by 2023, his official spokesman said.

According to the Spectator, the PM also told cabinet he was “the most liberal Conservative PM in decades”. At which point, Matt Hancock interjected, “Don’t tell Priti’, in reference to right-wing Home Secretary Priti Patel.

But Temerko, who has praised Johnson in the past, said the government’s domestic policies were “absolutely populist”, that “any party would do the same” in the run-up to an election, and that they amounted to “nothing new, nothing exciting”.

Speaking to HuffPost UK, the Ukrainian-born donor said: “There is only one slogan that the party today is fanatically promoting: that is leave Europe with or without a deal.

“October 31 is Boris Johnson’s day of death.

“Today the party is mostly not a centre ground party at all, it is turning more and more into a politically religious sect with just one idea – the idea of Brexit as the only one god.

“We are Christian or Muslim or Jewish – we have another god, Brexit is not our god.

“That is a big problem and the people who can keep the party in the centre ground are on the outside.”

He added: “It’s absolutely crucial if we want to be an attractive national party with a successful political future.”

Like many in the party, he criticised Johnson for suspending parliament until October 14 and suggested Cummings, the PM’s chief of staff, was behind the PM’s more extreme actions, including the purge of rebels.

“He is like the archbishop of this sect,” Temerko said of Cummings.

“He is like a spiritual leader of an inquisition inside the Conservative Party.”

Despite the criticism, Temerko said he would continue to give money to the party to keep out “another sect” – Jeremy Corbyn’s Labour.

“I support the Conservative Party,” he said.

“I totally agree with Philip Hammond, I will stay in the party to try and stop it becoming a nationalist party with a small, nationalist, separated, isolated agenda.”

But Temerko, who backed Jeremy Hunt for the Tory leadership, warned the party may not win a majority at the next election and so needs to be more moderate to be in a position to potentially form a coalition government, and for its long-term sustainability.

“The party is quite small, it’s 160,000 people, 70% of people are from the older generation – we cannot be a sect within a sect,” he said.

“We need new blood, the young generation, business, and definitely we need a broader agenda and a reasonable form of Brexit.

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