Rob Merrick www.independent.co.uk
Asked if it might “spook” the markets, he said: “There might be some concern about whether this was going to be a stable government again, given the instability that we had at the end of Johnson’s term as prime minister.
‘I think market participants might be concerned that, even if the fiscal statement coming up imminently goes off OK, there might be issues further down the road.”
The warning came as the interest rate demanded by investors buying government gilts rose sharply after Mr Johnson was installed as the bookies’ favourite to succeed Liz Truss.
It was soaring borrowing costs after Kwasi Kwarteng’s disastrous mini-Budget that forced the Bank of England into an emergency rescue – instability only brought to an end by dramatic U-turns on tax cuts.
Professor Bean said the Treasury must find £30bn of spending cuts or tax hikes to claim convincingly that it has a plan to get a grip on borrowing and debt.
Even if the savings are found, “there will then be a question of whether they can get a fractious Conservative Party to support all the measures”, he told BBC Radio 4.
The warning comes after a former cabinet secretary advised that the new prime minister must be in place by Tuesday to avoid the risk of a market backlash and higher interest rates.
A former Johnson aide and now critic of the former leader has said he is enjoying a surge in support among Tory MPs and has a “very” good chance of returning to No 10.
If he wins the support of 100 MPs and enters the race on Monday, it also increases the likelihood that it will last the week and go to a ballot of Tory members.
The Commons leader, who finished third in July’s leadership race, is likely to face Rishi Sunak and possibly Mr Johnson, but neither has made an announcement yet.
Ms Mordaunt is believed to have told Jeremy Hunt he will remain as chancellor, and that there will be no delay to his de facto Budget planned for 31 October.