Gavin Williamson was sacked as UK defense secretary after Theresa May was informed that he had attacked her in private, saying that her diabetes made her unfit to be prime minister, The Sunday Times reported.

May became frustrated with Williamson’s behavior after hearing that he told fellow Tories that her health meant she should not continue in the job—claims that Williamson rejects as categorically untrue.

The warnings were delivered in the weeks before Williamson was dismissed amid claims that he leaked details of a National Security Council meeting last month.