Speaking ahead of the Prime Minister’s Tory Party Conference speech, the professor of politics at Strathclyde University said the Government’s recent tax cutting budget shakeup could do “serious damage” to their reputation for economic competence.
He added the swing among voters was worse for the Tories than in 1992 after Black Wednesday, when a collapse in the pound forced Britain to withdraw from the European Exchange Rate Mechanism.
“All of the ingredients for electoral defeat are in place,” Sir John told Sky News.
“The question is whether or not in the end, they are combined and put into the oven and thereby baked into the memories and perceptions of voters.
“We’ve now got on average across 10 opinion polls a 25 point lead for the Labour Party in the polls that represents no less than an 8 per cent swing from Conservative to Labour since the announcement of the fiscal statement last Friday week. “
“That is comparable to the swing that happened in September 1992 in the wake of Black Wednesday, which was the last time that a conservative administration got into trouble with the financial markets. Then the swing was 7.5 per cent and only after a month had elapsed.
“The second thing that happened in the wake of Black Wednesday, an event from which that Conservative government never recovered laterally is a serious damage to the Conservatives reputation of economic competence.”
The pound collapsed against the dollar last week after Chancellor Kwasi Kwarteng announced a series of tax cuts in a bid to boost economic growth.
Mortgage products were pulled from the market over interest rate fears, and the Bank of England stepped in and said it would buy back up to £65bn of gilts in a bid to stabilise the market and protect pensions.
Earlier this week the government U-turned on plans to scrap the 45p rate of income tax for higher earners following an outcry.
During her conference speech, Liz Truss will say the “disruption” from her plans to revive the country’s economy will be worth it as she battles to save her premiership after just a month in the job.
She will insist there can be no more “drift and delay” in the effort to boost economic growth and defend her “new approach” which will “unleash the full potential of our great country”.
The Prime Minister, who was only elected as Tory leader on September 5, will tell activists in Birmingham that she hopes to create a “new Britain for a new era”, with an unashamedly pro-growth strategy – even though not everyone will be in favour of her methods.
Ms Truss will say: “For too long, our economy has not grown as strongly as it should have done.
“For too long, the political debate has been dominated by how we distribute a limited economic pie. Instead, we need to grow the pie so that everyone gets a bigger slice.
“That is why I am determined to take a new approach and break us out of this high-tax, low-growth cycle. That is what our plan is about: getting our economy growing and rebuilding Britain through reform.”