British Prime Minister Theresa May's "excruciating" conference speech dominated Thursday's newspapers, which had sympathy for her bad luck but bleak warnings about what the string of misfortunes signalled for her leadership.

"May on final warning after speech shambles -- Tory dismay as PM falls victim to prank, coughing fits and faulty set," said the Times headline.

May was hoping to use the Conservative Party conference speech to reassert her authority following a dismal election showing, but was interrupted by a comedian handing her a notice of unemployment before succumbing to a persistent cough in front of a collapsing set.

"A leader's conference speech should be an affirmation of purpose and authority," said the centre-right paper's editorial.

"Theresa May projected little of either in Manchester. She united the Conservatives in sympathy when what she needed was authority. She must soldier on, on borrowed time."

Popular tabloid The Sun carried a front-page picture of the sign behind May, which fell apart as she spoke, above the headline "PM's nightmare as sign collapses."

"No one can fault Theresa May's courage," said the paper. 

"It was impossible not to admire her for ploughing on gamely. What worries is us the lack of ambition in what she said. The Tories need a truly game-changing idea, depressingly, Mrs May hasn't found it yet".

May made light of her coughing attack, tweeting a picture of a range of cold remedies underneath the caption *cough*.

The Daily Mail, usually supportive of May, carried a double page spread of photographs documenting the disaster, under the headline "every cough and spit of that nightmare speech".

Even the left-wing Guardian had some sympathy, calling it "an excruciating public agony" in its editorial.

"The prime minister handled that shock (stage invader) with aplomb, but her ensuing coughing fits and losses of voice, surely triggered by the interruption, threatened to make the speech almost impossible to watch or listen to. 

"It is almost inevitable that the distractions will unfairly damage Mrs May, reinforcing her vulnerability and her image as an accident-prone loser," it added.

The centre-right Daily Telegraph headline read "Luckless May centre stage in tragic farce".

The paper carried a front-page piece from its parliamentary sketchwriter, which said: "Weeks, months, even years from now, perhaps for the rest of my life, I will still be jolting awake in the night: heart pounding, pyjamas soaked in sweat, and lungs gasping frantically for breath, as I relive, in agonising slow-motion, the full screaming nightmare of that speech."