Boris Johnson is not "in charge" of his own government and has no real plan for government, Ken Clarke has said.
In an astonishing attack on the prime minister, the former Tory chancellor said Mr Johnson did not know what he wanted to do with his new governing majority and could not simply go around saying 'Oooh 2020 is going to be a golden year'.
Mr Clarke contrasted Mr Johnson with Margaret Thatcher, who he said had an even bigger Commons majority and "knew exactly what she was going to do" with it.
The Tory grandee was expelled from the Conservative Party by Mr Johnson after rebelling on Brexit, and stepped down at the election after 49 years as an MP.
Speaking to the BBC, he claimed that the government was being run not by Mr Johnson but by the prime minister's senior adviser, Dominic Cummings.
He told 5Live's Pienaar's Politics: "The optimistic side of me thinks if Boris does read the brief and now gives some serious thought to what he wants to do now he is prime minister. You never know, he could turn out to be a very sound, moderate, One Nation Conservative.
"Boris could still surprise everybody. But at the moment, when I read the newspapers, Dominic Cummings seems to be briefing the newspapers on his own personal agenda and says the government is going to re-organise departments, tackle Ministry of Defence procurement - well, I agree with that, that needs tackling - and so on.
"I don't get the impression that politicians are in charge, together with someone who knows something about governing."
Asked about Mr Johnson's plan for government, Mr Clarke replied: "He hasn't got one."
He continued: "It needs more detail. The excitement, the adrenaline of the campaigning, is still there and he's still surrounded by all the people around the campaign. I don't get the impression that they've yet pressed the governing button.
"They've now got five years and certainly for the first two or three they can do whatever they want. Do they know what they want, and are they prepared for that?
He added: "The governing of the country is more than going round saying, 'Oooh, 2020 is going to be a golden year, we are going to be a global Britain'.
"At the moment we have a stagnant, fragile economy; an angry discontent population, particularly the white working class in the North and north Midlands where I am."
Mr Clarke said the Conservative had no policy on social care, which he called "the biggest single domestic problem facing us" and needed to do more to improve skills and education across the country.