In a joint statement to Daily Telegraph with the Tees Valley mayor, he says Johnson would lead “a broad-based, inclusive government drawing on talent from right across the Conservative Party, driven by a disciplined Downing Street”.
Business Secretary Jacob Rees-Mogg has already backed Johnson, while Defence Secretary Ben Wallace said he was “leaning” towards supporting him.
Clarke, a Truss loyalist, said Johnson “is the person we need to lead our country and our party” as he can unite the UK, make Brexit a success, and control illegal immigration.
No one has yet confirmed they are entering the race, but the BBC’s latest tally suggests Rishi Sunak would have the backing of 56 MPs, Johnson would have 33 and Penny Mordaunt would be on 17.