Coughs and a protest mar Theresa May's speech

Comedian Lee Nelson - real name Simon Brodkin - joked that Foreign Secretary Boris Johnson had asked him to perform the stunt.

It led to frantic scenes as he was bundled out of the conference hall and through the exhibition stands by security staff at the Manchester Central venue.

The incident took place midway through a conference speech that also saw the Prime Minister battle through repeated fits of coughing, and ended with her receiving a standing ovation from Tory activists as sections of the main stage backdrop collapsed.

It has led to calls for an investigation as to how Nelson was allowed to get so close to the Prime Minister, with Dudley South MP Mike Wood describing the incident as 'extremely worrying'.

The intrusion threatened to overshadow a speech in which Mrs May announced new council houses and a cap on energy prices as part of a bid to 'renew the British dream'.

Following his prank, Nelson, who is due to play dates in Wolverhampton, Walsall, Dudley and Shrewsbury in the coming weeks, told reporters: "Boris told me to do it. He's left me in the lurch."

The 'P45' he handed to the Prime Minister gave the 'reason for termination' as: "Neither strong or stable. We're a bit worried about Jezza."

It is understood that Nelson joined the Conservative Party earlier this year and formally applied to attend the conference.

He rose to prominence in 2015 when he showered scandal-hit Fifa president Sepp Blatter with money at a press conference.

He was given a conditional caution after he duped security at Manchester City's game at Everton in March 2013 and warmed up on the pitch alongside star players.

Mr Wood, who was in the hall watching the speech when the incident occurred, said: "I'm very surprised that he was able to get so close to the stage without being stopped by security.

"Serious questions must be asked. As delegates we have to apply to attend the conference months in advance and go through stringent security checks.

"It is extremely worrying how easily he was allowed to disrupt the Prime Minister's speech and I can only hope there is a thorough investigation into the full circumstances behind this unfortunate incident."

Home Secretary Amber Rudd said the Government was now 'carefully' looking into what she described as a 'disappointing stunt'.

For her part the Prime Minister did her best to laugh off the intrusion, joking that the only P45 she wanted to give out was to Jeremy Corbyn.

But she struggled to finish her speech due to an intermittent cough. She had to stop several times to drink water and at one point she was handed a cough sweet by Chancellor Philip Hammond.

Mrs May apologised to delegates for an election campaign that had been 'too scripted, too presidential'.

The Prime Minister said the 'British dream' that 'life should be better for the next generation' was out of reach for too many people, something she vowed to dedicating her premiership to fixing.

Hailing plans to 'reignite home ownership' in Britain, she said the Government plans to invest an additional £2 billion in affordable housing, taking the total budget up to almost £9bn.

She urged the party to focus on the needs of working people, insisting it should be 'not addressing our concerns, but the issues, the problems, the challenges, that concern them'.

She also announced that the Government will next week publish draft legislation to impose a cap on energy prices.

Cabinet ministers rallied round Mrs May following her speech.

Health Secretary Jeremy Hunt said he believed her efforts showed a 'great sense of duty', while Environment Secretary Michael Gove said: "I thought it was a fantastic speech from a Prime Minister at the top of her game."

Senior MP George Freeman, head of the Prime Minister's policy board, described it as the 'most electrifying' speech and added Mrs May's 'faltering' voice heightened the sense of her tenacity.

"She completely turned around that tone of the general election, of a monotone, iron lady, the Maybot," he said.

"This was a woman showing her vulnerability, showing her frailty, and in so doing connecting with and demonstrating what is her greatest strength - a steely commitment to public service, an incredible personal sense of duty, a woman who at an age of life where many would be putting their feet up, is redoubling her commitment to the toughest job in the country.

"Strangely, the faltering voice actually heightened the sense of her tenacity and her commitment to go through the adversity.

"You could feel the more she spoke, the more the mood came with her, as people celebrated the values of public service that are at the heart of Conservatism.

"You couldn't have scripted it more powerfully."