Liz Truss will today admit she was in a rush to get results with her disastrous mini-budget and was “forced into a policy reversal under the threat of a UK meltdown”.

Ahead of the first anniversary of the event that helped end her premiership after just 49 days, the former PM will also lecture her successor on the economy.

In a speech at the Institute for Government, she will urge Rishi Sunak’s government to cut taxes, shrink welfare spending and raise the retirement age.

The Tory leadership should embrace free market ideologies and ditch some green commitments amid cost-of-living pressures on voters, she will say.

Ms Truss will also defend decisions she made while in Number10, denying she pursued “unfunded” tax cuts by citing the work of a consultancy founded by an ally.

Ms Truss was forced out of office last October after the September mini-budget set out by her chancellor Kwasi Kwarteng sparked an economic crisis.

Markets baulked at its £45billion of tax cuts and the lack of Office for Budget Responsibility sign-off, leading to a slump in the pound. 

Billed as her first significant intervention on the economy since Tory MPs lost confidence in her and forced her out of Downing Street, Ms Truss will say: “Some people have described these as ‘unfunded tax cuts’. This is not a fair or accurate description.

“These tax cuts could have increased funding for our public services.”

She will claim Mr Sunak has spent £35bn more than she would have as PM, arguing that if her policies had been followed, growth would have eventually been higher.

“Investment would not have faltered in the North Sea, were it not for the windfall tax. We would have got moving on fracking and lower energy bills would now be on the horizon.

“A more competitive rate of corporation tax would have persuaded the likes of AstraZeneca not to relocate elsewhere. There would have been more duty-free shoppers and a boom in the number of self-employed.”

Attacking the “anti-growth coalition”, Ms Truss will claim her plan was stymied by reaction from “the political and economic establishment which fed into the markets”.

But she will concede that she and Mr Kwarteng were in a “rush” to get “results”.

She will say: “I was effectively forced into a policy reversal under the threat of a UK meltdown. It is certainly true that I didn’t just try to fatten the pig on market day; I tried to rear the pig and slaughter it as well. I confess to that.”

Chancellor Jeremy Hunt is currently preparing for the Autumn Statement, but tax cuts have repeatedly been ruled out while inflation remains high.

Ms Truss will label that a mistake and call for a swathe of cuts, including taking corporation tax back to 19%, reforming marginal tax rates, and abolishing the windfall tax.

She will add: “We need to get a grip on the ballooning welfare and pensions bill. 

“This means slowing the rate of increases to benefits and tougher work requirements. It also means raising the retirement age further.

“We should… delay implementing net zero commitments such as the ban on new petrol and diesel vehicles from 2030. Other environmental regulations which are hiking the cost of living, like enforcing the replacement of gas and oil boilers, should also be abandoned.”

Liberal Democrat deputy leader Daisy Cooper said: “Liz Truss giving a speech on economic growth is like an arsonist giving a talk on fire safety.”

Labour frontbencher Jonathan Ashworth wrote to the Prime Minister calling on him to block Ms Truss’s yet-to-be published resignation honours list.

He wrote: “It has been widely reported that Liz Truss has submitted up to 14 people to receive resignation honours. This means that those who crashed the economy, who left millions to pay more for their mortgage and who undermined our economic institutions could receive an award. I urge you to block these honours.”