Robert Jenrick has been sacked from the shadow cabinet and suspended from the Conservative party after Kemi Badenoch said she was presented with “irrefutable evidence” that he was planning to defect from the party.

The shadow justice secretary was Badenoch’s leadership rival and had long been said to be prepared do a deal with Nigel Farage’s Reform UK.

Badenoch did not name the party to which Jenrick was planning to defect, but sources confirmed it was Reform UK, and criticised him for putting personal ambition above loyalty. Farage is due to give a press conference in Westminster on Thursday afternoon.

Westminster sources said Badenoch had been monitoring Jenrick’s activities for some time because of suspicions he was working to undermine the party and they believed his defection to Reform was imminent.

They said their concerns were confirmed by the indiscreet activities of some of Jenrick’s unofficial aides, known internally as the “grid of shit” plotters because of their efforts to depose Rishi Sunak.

Farage and Jenrick are understood to have had dinner last month, according to Tory sources.

Badenoch said in a statement: “I have sacked Robert Jenrick from the shadow cabinet, removed the whip and suspended his party membership with immediate effect.

“I was presented with clear, irrefutable evidence that he was plotting in secret to defect in a way designed to be as damaging as possible to his shadow cabinet colleagues and the wider Conservative party.

“The British public are tired of political psychodrama and so am I. They saw too much of it in the last government, they’re seeing too much of it in THIS government. I will not repeat those mistakes.”

Jenrick, a former immigration minister, has built a sizeable social media following, and any potential move to Reform would be the most high-profile defection so far for a sitting MP, after the previous move of the shadow minister Danny Kruger.

In a video posted on X, Badenoch said she was determined to end the vicious cycle in the Conservative party of constant betrayals. “When I was elected leader, I committed to doing politics differently. Disloyalty and dishonesty undermine trust in politics,” she said.

“When individuals choose to walk away from that effort for personal ambition, that tells you nothing about the Conservative party and everything you need to know about them.”

Speaking in Scotland earlier on Thursday, Farage has said that “of course” he had had conversations with Jenrick. “Was I on the verge of signing a document with him? No. But have we had conversations? Yes.”