Boris Johnson has until the autumn to save his premiership, his former Brexit minister Lord Frost has warned.
The prime minister must set out a clear Conservative vision of the future or face being ousted by his own MPs, he said.
Mr Johnson narrowly survived a confidence vote on Monday, with 41% of his own MPs voting against him, a result which will severely undermine his leadership.
In an article for The Daily Telegraph, Lord Frost – who was once one of Mr Johnson’s closest advisers but is now among his most trenchant critics – said the prime minister could not afford to ignore the “depth of opposition” he faces within his own party.
He said the biggest problem the government now faces was not the issue of lockdown parties in Downing Street, but that voters did not understand what it was trying to do.
“Every prime minister has weaknesses and blind spots. The issue is whether they are able to compensate for them, by having the right people, by taking good advice, and by setting a clear policy direction with broad support,” he said.
“Mr Johnson probably has between now and the party conference to show he can do that.”
Lord Frost said the government needed a clear “Conservative plan” based on “freedom and individual liberty not collectivism”.
He said that instead it looked like the government was constantly at risk of being swamped by a series of crises it was having to deal with.
“Like the cockpit of a crashing airliner, the dashboard lights are all flashing red. The government has to decide which problems must be dealt with now and which can be left until later,” he said.
He recommended that ministers focus on reversing tax increases, “credibly” commit to future cuts, slash VAT on energy bills and open up fracking.
He called on Mr Johnson to carry out a cabinet reshuffle and appoint a “serious deputy” who could “design and deliver the strategy”.
“This is ambitious. I can see why many people think the prime minister can’t deliver it. He doesn’t like upsetting people. But any serious plan means making choices,” he said.
“Many of us still want him to succeed and will support him if he shows a sense of purpose. But he has to show things will be different now.”
It comes as a top government adviser known as Britain’s strictest headmistress said Mr Johnson was not a good role model for children.
Katharine Birbalsingh, chair of the social mobility commission, told Sky’s political editor Beth Rigby that from his personal life to his messy hairstyle, the prime minister causes her to “raise an eyebrow”.