Theresa May’s keynote speech descended into farce on the final day of Conservative conference after a comedian’s stunt and a relentless coughing fit laid waste to hopes it would rejuvenate her embattled leadership.

During a delivery that was at times difficult to watch, a prankster handed her a P45 in front of hundreds of party members and there were uncomfortable pauses as she repeatedly lost her voice, before croaking and coughing through long sections.

The performance approached the ridiculous, when letters began falling off the sign bearing the Conservative party’s slogan on the set behind her.

Cabinet members applauded, but at times looked mortified – in one scene captured on camera, Home Secretary Amber Rudd appeared to demand Boris Johnson stand and clap.

Afterwards, Ms May’s spokesman claimed she was happy with how it had gone, but her aides were later forced to deny reports the Prime Minister had left the stage and wept.

The unfortunate series of incidents will dismay Conservatives, as coverage of the debacle will inevitably distract from the key policies announced on housing, energy bills and organ donation along with her words on Brexit.

Ms May has said she wants to fight the next election, but the speech was already causing some Tory MPs to ask whether she is the best candidate to lead them through to Christmas, let alone 2022.

Tory conference 2017 – in pictures Show all 23 1 /23 Tory conference 2017 – in pictures Tory conference 2017 – in pictures Comedian Simon Brodkin hands Theresa May a p45 during her conference speech @simonbrodkin/Twitter screengrab Tory conference 2017 – in pictures Britain's Prime Minister Theresa May struggles with her water after she suffered a coughing fit whilst addressing the Conservative Party conference in Manchester Reuters Tory conference 2017 – in pictures Britain's Foreign Secretary Boris Johnson delivers his speech on the third day of the Conservative Party annual conference Tory conference 2017 – in pictures Bear Grylls at the Conservative party conference at the Manchester Central Convention Complex PA Tory conference 2017 – in pictures Britain's International Development Secretary Priti Patel gestures after delivering her speech on the third day of the Conservative Party conference Paul Ellis/AFP Tory conference 2017 – in pictures Prime Minister Theresa May and Chancellor Philip Hammond visit a home in Manchester during the Conservative Party conference in the city Phil Noble/PA Tory conference 2017 – in pictures Britain's Foreign Secretary Boris Johnson returns from a morning run on the second day of the Conservative Party Conference, in Manchester Reuters/Phil Noble Tory conference 2017 – in pictures Delegates view a display board showing the history of the Conservative Party as they arrive for the first day of the annual Conservative Party conference Getty Tory conference 2017 – in pictures Delegates carry pro-Brexit bags as they arrive for the first day of the annual Conservative Party conference Getty Tory conference 2017 – in pictures Delegates listen to Justine Greening's speech on the first day of conference Carl Court/Getty Tory conference 2017 – in pictures Britain's Prime Minister Theresa May and her husband Philip applaud a speaker on the first day of the annual Conservative Party conference Carl Court/Getty Tory conference 2017 – in pictures Scottish Conservative leader Ruth Davidson speaks at the Conservative Party Conference at the Manchester Central Convention Complex PA Tory conference 2017 – in pictures Secretary of State for Education, Justine Greening, speaks on the first day of the conference Carl Court/Getty Tory conference 2017 – in pictures Chairman of the Conservative Party, Patrick McLoughlin, speaks at the opening of the first day of the Tory party conference Tory conference 2017 – in pictures Chancellor of the Exchequer, Philip Hammond, arrives for the first day of Tory party conference Carl Court/Getty Tory conference 2017 – in pictures Secretary of State for Defence, Michael Fallon, arrives at conference Getty Tory conference 2017 – in pictures Home Secretary, Amber Rudd (C), attends the first day of the Conservative Party conference Carl Court/Getty Tory conference 2017 – in pictures Secretary of State for Communities and Local Government, Sajid Javid, attends the first day of the Conservative Party conference Getty Tory conference 2017 – in pictures Former Conservative minister, Edwina Currie, at the first day of conference Carl Court/Getty Tory conference 2017 – in pictures Secretary of State for International Trade, Liam Fox, arrives at conference Carl Court/Getty Tory conference 2017 – in pictures Britain's Foreign Secretary, Boris Johnson, arrives at the conference hotel for the Conservative Party Conference Reuters/Darren Staples Tory conference 2017 – in pictures The anti-Tory march makes its way to the Conservative party conference in Manchester Peter Byrne/PA Tory conference 2017 – in pictures A demonstrator walks a dog wearing a European Union flag during a protest on the opening day of the Conservative Party Conference, in Manchester Reuters/Darren Staples

Going into the speech, Ms May had seemingly managed to prevent her authority eroding further after a fortnight in which speculation about a leadership challenge from Mr Johnson had mounted.

All her ministers, including the Foreign Secretary, had thrown their weight behind her during conference speeches and she had a raft of policy announcements to make, in a bid to refocus the political narrative on her plans for government.

But shortly into her speech a furore broke out when comedian Simon Brodkin – known for his Lee Nelson character – approached the stage and handed her a P45 unemployment notice.

Amid frantic scenes he was bundled out of the conference hall and through the exhibition stands by security staff at the Manchester Central venue, telling reporters: “Boris told me to do it. He’s left me in the lurch.”

Simon Brodkin speaks to Boris Johnson (Getty)

Inside the hall, Ms May fought to prevent the speech becoming a presentational nightmare, responding quickly by saying that she would have liked to give a P45 to Jeremy Corbyn, winning a cheer from the crowd.

Brodkin was arrested, but the prank raised serious security questions as to how someone not supposed to be in the tightly guarded centre gained a pass and was able to get within centimetres of the Prime Minister, Foreign Secretary and Home Secretary.

Police immediately launched an investigation and a review of the accreditation system all attendees to the conference must go through.

But it was disruption to Ms May’s speech that will be more damaging to the Prime Minister in the short term. She was already starting to suffer from a dry cough when the prankster hit, but afterwards her condition deteriorated, leaving her struggling to raise words to her lips.

Theresa May's speech breaks down due to coughing fit

The first time she completely lost her voice, the crowd rallied, giving her a prolonged standing ovation and cheering, allowing time for an aide to refill her water glass and for a cough sweet to be delivered to the podium courtesy of Chancellor Philip Hammond.

Ms May also tried to dismiss the mishap with a joke about how she had received something free from the Chancellor, giving hope that she might turn the situation round.

But despite her best efforts, her ailment returned with a vengeance, again leaving her desperately trying to clear her throat and fighting to keep her voice.

Cabinet ministers laughed at her jokes and joined applause, but in one moment that could be an enduring image from the speech, a standing Ms Rudd turned to a sitting Mr Johnson, spoke tersely and appeared to wave a hand signalling for him and others to stand.

Letters fall off Tory slogan behind Theresa May during conference speech

The crowd also rallied again to support the Prime Minister giving her applause for cover, but as the spectacle continued gasps and sighs could be heard from some members of audience.

As she fought through to the end of the address, an “F” fell off the slogan “building a country that works for everyone”, followed shortly after by the “E” at the end of the sentence.

A spokesman was asked afterwards, how the PM felt about the event, replying: “Good. It was a good speech. She was happy with the way it went.”

He explained that Ms May was suffering from “a conference cold”, and went on: “Since she’s been here she’s done 28 interviews and and she’s done 19 receptions and that’s taken its toll on her voice.”

Work and Pensions Secretary David Gauke told The Independent : “Not for the first time, the Prime Minister showed courage and resilience.

“Her determination to deliver for the British people was clearly demonstrated in the words and delivery of her speech with these important policy announcements.”

When Mr Hammond was asked about the coughing, he said: “She showed her resilience, and displayed her personal commitment to the job she is doing.

“She gave the audience a glimpse of why she feels so passionate about doing the things she is doing. Obviously nobody wants to be coughing in the middle of a speech. That was unfortunate.

“But she got over it, she showed her resilience and she delivered the speech.”

Brexit Secretary David Davis said: “She is a very tough, resilient lady who dealt with it brilliantly and that’s the most important thing and that is what the public will see.”

Mr Davis called the security breach “extraordinary” with both he and party chair Patrick McLoughlin saying it would be investigated.

Ministers called Ms May to offer backing following the address, but backbench MP Mark Pritchard suggested a “small number” of colleagues were raising questions over her leadership in text messages and warned them “there is no vacancy at Number 10”.

Senior Conservative MP George Freeman, head of the Prime Minister’s policy board, went even further in defending the PM, describing the speech as the “most electrifying” he had seen and arguing that her “faltering” voice had heightened the sense of her tenacity.

He said: “She completely turned around that tone of the general election, of a monotone, iron lady, the Maybot.

“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.”

During the speech Ms May admitted millions of Britons feel deprived of things their parents took for granted and apologised for the general election result saying her campaign had been “too scripted, too presidential”.

She told her party faithful: “I hold my hands up for that. I take responsibility. I led the campaign.”

She also admitted the house price explosion had been “a disaster for young people” as she unveiled new measures in a bid to provide more affordable homes to rent and buy.