Sir Keir Starmer demanded a general election “now” after Liz Truss quit, and said Labour is “very prepared” with a manifesto ready to go.

In the wake of Ms Truss’s resignation as Tory leader after a chaotic 44 days in office, the Labour leader said: “After 12 years of Tory failure, the British people deserve so much better than this revolving door of chaos”.

He said the Conservatives “do not have a mandate to put the country through yet another experiment” and that the British public “deserve a proper say” on the country’s future.

The Tory party will now scramble to find a replacement for Ms Truss, with that person to become its third leader in two months.

Sir Keir said: “There is an alternative and that’s a stable Labour government and the public are entitled to have their say and that’s why there should be a general election”.

If that does happen, Labour is primed, he said.

“There’s a manifesto that is going to be ready whenever an election is called,” Sir Keir told the BBC’s Newscast podcast.

“I’ve had a team working on that. I’ve had a team working on general election preparedness. We’ve moved our teams on to a general election footing. And I’ve got in place all the grids I need for a general election. So we’re very, very prepared should there be a general election.”

On speculation that Boris Johnson could attempt a comeback, Sir Keir said the former prime minister was “unfit for office”.

“Let’s remember that it was three months ago pretty much that he resigned in disgrace,” he said.

“So if they’re going to go from this experiment, this chaos, this economic damage, (and) wind back three months to a man who was deemed to be unfit for office, I think that only adds insult to injury for the public (who will be) knocking on the door saying, ‘Hang on, why can’t we have a say on this?’”

Hours earlier, before Ms Truss’s resignation, Sir Keir used his address at the annual Trades Union Congress (TUC) conference in Brighton to lambast the “pathetic squabbles” in her Government.

The speech came after a calamitous day for Ms Truss’s premiership which saw a cabinet minister resign and an open revolt in the Commons.

Sir Keir began his speech by making reference to the chaos in Westminster.

“With everything going on, I’m a bit nervous to turn my phone off for half an hour or 45 minutes,” he said.

“We really don’t know what will have happened by the time we turn it back on.”

He said the events in Parliament the evening before had been “even by their standards, a new chaotic low”.

Sir Keir said that his own sister, a care worker, “struggles to make ends meet” amid the cost-of-living crisis.

“The Prime Minister is completely out of touch with the reality of the British economy,” Sir Keir said.

“Working people will not be better off because we make the rich, richer.

“It’s pure dogma – the world has moved on from these discredited ideas. And every day the Tories stick to them, is another nail in the coffin of Britain’s economic credibility…

“Never again can Britain take seriously their claim to be a party of aspiration or sound money.”

At the same time Sir Keir warned that the damage inflicted on the public finances by Ms Truss’s Government would mean that a Labour government would face difficult decisions if it was to restore confidence in the UK economy.

“Things are going to be really tough now and during my Labour government,” he said, stressing that Labour would be “the party of sound money” and take no “risks” with the public finances.

“When you lose control of the economy, as the Tories have done, you lose the ability to do anything and working people pay the price. That will not happen with Labour, I will not let it.”

He vowed that a government led by him would “put this Tory trickle-down nonsense back in its box once and for all”.

Unite union general secretary Sharon Graham said Labour must convey a “clear and action-based” message to show Britons what they can vote for.

“Warm words are welcome, but we now need a message from Labour that is clear and action-based that shows the country what they can vote for, not just what they should vote against,” she said.