Former Home Secretary Suella Braverman has accused Rishi Sunak of repeatedly failing to deliver on key policies.
BBC News at Six is reporting that in a scathing letter to the prime minister, Mrs Braverman told him “your plan is not working”.
She said Mr Sunak had betrayed his pledge to do “whatever it takes” to stop small boats crossing the Channel.
Mrs Braverman, a leading figure on the right of the party, was sacked as home secretary on Monday, kick-starting a major cabinet reshuffle.
A No 10 spokesman thanked Mrs Braverman for her service, but added: “The prime minister was proud to appoint a strong, united team yesterday focused on delivering for the British people.” In her letter, the former home secretary told the prime minister he had “manifestly and repeatedly” failed to deliver on policy priorities.
“Either your distinctive style of government means you are incapable of doing so,” she wrote.
“Or, as I must surely conclude now, you never had any intention of keeping your promises.”
She added: “Someone needs to be honest: your plan is not working, we have endured record election defeats, your resets have failed and we are running out of time. You need to change course urgently.”
Mrs Braverman was sacked from her role, after opponents accused her of stoking tensions ahead of pro-Palestinian marches in London.
She lost her job days after she claimed police had applied a “double standard” to protesters, in an article for the Times newspaper.
Mrs Braverman said Mr Sunak had failed “to rise to the challenge posed by the increasingly vicious antisemitism and extremism displayed on our streets”.
“I have become hoarse urging you to consider legislation to ban the hate marches and help stem the rising tide of racism, intimidation and terrorist glorification threatening community cohesion,” she added, accusing the PM of putting off “tough decisions in order to minimise political risk to yourself”.
In her letter, Mrs Braverman says she had agreed several conditions with Mr Sunak when she took up the role in October 2022, which were outlined in a document.
Sources close to Mrs Braverman claim Mr Sunak read and agreed the document the letter refers to, which had been drawn up by Mrs Braverman.
They say he took a copy and there were witnesses.
The letter comes ahead of a crucial ruling on Wednesday, when the Supreme Court will decide on the lawfulness of the government’s plans to send some asylum seekers to Rwanda.
Mrs Braverman told the PM that if the ruling went against the government, he would have “wasted a year” on the Illegal Migration Act, which aimed to stop small boat crossings, “only to arrive back at square one”.
“Worse than this, your magical thinking – believing that you can will your way through this without upsetting polite opinion – has meant you have failed to prepare any sort of credible ‘Plan B’.”
She said she posed her own back-up plan but received no reply.
A No 10 spokesman said the government had “brought forward the toughest legislation to tackle illegal migration this country has seen and has subsequently reduced the number of boat crossings by a third this year”.
“And whatever the outcome of the Supreme Court tomorrow, he will continue that work,” the spokesman added