This is what his own team think of him...
"Dear Boris,
"As you know, I have supported you throughout your career in politics: for Mayor of London in 2007-8 and 2012 and for Leader in 2016 and 2019.
"As Prime Minister you have been dealt a very difficult hand with Covid and Ukraine, and you deserve great credit for much of the way in which the Government has handled these twin crises. Your recent visit to Kyiv was a conspicuous act of leadership.
"When I stepped down from the Treasury last September, you raised the topic of the next reshuffle, and we discussed the potential for me to run a department of state.
"I have always been deeply committed to public service. But recent events have served to clarify the position this country is in under your leadership, beyond any doubt; and I am afraid I can see no circumstance in which I could serve in a government led by you.
"First, as Sue Gray's report underlines, you have presided over a culture of casual law-breaking at 10 Downing Street in relation to Covid. To describe yourself as "vindicated" by the report is grotesque.
"Secondly, both in the Queen's Speech and elsewhere, your current policy priorities are deeply questionable. Breach of the Northern Ireland Protocol would be economically very damaging, politically foolhardy, and almost certainly illegal.
"You are the leader of the Conservative and Unionist party, yet you are putting the Union itself gravely at risk.
"The Rwanda policy is ugly, likely to be counterproductive and of doubtful legality. Privatisation of Channel 4 is an unnecessary and provocative attempt to address a political non-issue during a time of crisis, at significant cost to the independent UK film and TV industry.
"No genuinely Conservative government should have supported the recent ban on noisy protest - least of all when basic human freedoms are facing the threat of extinction in Ukraine.
"Thirdly, under you the Government seems to lack a sense of mission. It has a large majority, but no long-term plan. There is no sign, for example, that it has even begun to get to grips with the need for greater security and resilience in a range of policy areas.
"Rather, you are simply seeking to campaign, to keep changing the subject and to create political and cultural dividing lines mainly for your advantage, at a time when the economy is struggling, inflation is soaring and growth is anaemic at best.
"Sensible planning has been replaced by empty rhetoric. As a former Energy Minister I can tell you that there is, for example, zero chance that this or any government will be able to build a nuclear power station a year at any point in the next decade.
"Worse still: you are apparently trying to import elements of a presidential system of government that is entirely foreign to our constitution and law.
"But you are not a president, and you have no mandate other that as an MP, and from the confidence of your colleagues. Attempts to centralise powers in 10 Downing Street are not merely yet another ill-advised political distraction, but almost certain to compound and accelerate the problems listed above.
"In my judgement, all these things are at odds with a decent, proper conservatism: with effective teamwork, careful reform, a sense of integrity, respect for the rule of law and a long-term focus on the public good.
"Neither the Conservative party nor this country can afford to squander the next two years adrift and distracted by endless debate about you and your leadership.
"For you to prolong this charade by remaining in office not only insults the electorate, and the tens of thousands of people who support, volunteer, represent, and campaign for our party; it makes a decisive change of government at the next election much more likely. This is potentially catastrophic for the country.
"For these reasons, and with great sadness, I am withdrawing my support for you as leader, and I have notified this to the Chairman of the 1922 Committee.
"I leave it to our colleagues to decide where they stand in relation to these concerns. For the avoidance of doubt, however, this is not a leadership bid.
"As ever, Jesse"