Dominic Cummings has accused Boris Johnson of “possibly illegal” behaviour by “secretly” using Tory donors to pay for the renovation of his flat at Number 11 Downing Street, in an extraordinary broadside from the prime minister’s former top adviser. In a blog published on Friday evening, Cummings — who quit Number 10 in December — claimed that he had refused to help organise the payments. “The PM stopped speaking to me about this matter in 2020 as I told him I thought his plans to have donors secretly pay for the renovation were unethical, foolish, possibly illegal and almost certainly broke the rules on proper disclosure of political donations if conducted in the way he intended,” he wrote. “My knowledge about them is therefore limited.” Number 10 has repeatedly refused to deny that the cost of the project — thought to be up to £200,000 — was funded by the Conservative party and Tory donors. The work on the renovation has been overseen by Carrie Symonds, the prime minister’s fiancé. Previous prime ministers have received about £30,000 apiece to spend on decorating the flat to their own liking. Cummings also claimed on his blog that Johnson sought to abandon an inquiry into a leak last autumn about plans for a new Covid lockdown when its findings suggested Henry Newman, now one of Johnson’s advisers, may have been the source. “The PM was very upset about this,” Cummings wrote. “He said to me afterwards, if Newman is confirmed as the leaker then I will have to fire him, and this will cause me very serious problems with Carrie as they’re best friends . . .[pause] perhaps we could get the cabinet secretary to stop the leak inquiry?” Cummings claimed that he told Johnson that this would be “mad” and unethical given that the prime minister had ordered the inquiry and authorised the cabinet secretary to use “more invasive” methods than usual. “I told him that he could not possibly cancel an inquiry about a leak that affected millions of people, just because it might implicate his girlfriend’s friends,” he wrote. “It is sad to see the PM and his office fall so far below the standards of competence and integrity the country deserves,” he added. Cummings also used the blog to deny being the source of Johnson’s leaked text communications with industrialist Sir James Dyson, which were reported by the BBC earlier this week. The former adviser responded after three newspapers claimed on Friday morning that the prime minister was angry and disappointed with him for being the apparent source of the leak. “I was not directly or indirectly a/the source for the BBC/Kuenssberg story on the PM/Dyson texts,” Cummings wrote on his blog. More to come . . .