As he resigned, Lord Agnew insisted: “It is worth saying that none of this related to far more dramatic political events being played out across Westminster. This is not an attack on the Prime Minister and I am sorry for the inconvenience it will cause.”

However, his criticism of the Treasury may reflect badly on Rishi Sunak, the Chancellor, who is seen as a leadership frontrunner – with Ms Truss his chief competition.

Lord Agnew was appointed as a minister of state in 2020 with a brief to deliver public sector reform and efficiency, as well as supporting the Chancellor of the Duchy of Lancaster – at the time Mr Gove – with oversight of spending controls which operated across both the Cabinet Office and the Treasury.

He is also a former donor to the Conservative Party, giving £134,000 between 2007 and 2009.