Boris Johnson's poll leads vanish as loud altercation with partner deals major blow to Tory leadership bid

Boris Johnson’s poll ratings have suffered a major slump following the loud altercation with his girlfriend, as voters say his private life does matter in the race for No 10.

The favourite’s lead among Conservative voters has more than halved since the incident in the early hours of Friday morning – and rival Jeremy Hunt has snatched the lead among the wider public.

More than half of voters said Mr Johnson's private life was relevant to his ability to be prime minister and three-quarters said a candidate's character was relevant to the contest.

“It is unusual to see a politician's private life having this level of salience among voters,” said Damian Lyons Lowe, chief executive of pollsters Survation.

Mr Johnson has refused to give an explanation for the banging and screaming heard at the flat he shares with Carrie Symonds, despite it casting a shadow over his bid for No.10.

Instead, Mr Johnson insisted an audience of Conservative members at the first hustings of the Tory leadership race wanted to know “what my plans are for my country and for the party”.

“I don’t think they want to hear about that kind of thing,” the former foreign secretary claimed, speaking in Birmingham.

But the survey, for The Mail on Sunday, found that Mr Johnson's lead among Tory voters as the man who would make the best prime minister has more than halved, from a 27-point lead to just 11.

Survation carried out the second poll on Saturday – after the incident was revealed – whereas its first survey was completed on Thursday.

Among all voters, 36 per cent backed Mr Johnson and just 28 per cent supported Mr Hunt before the bust up, but the second survey put Mr Johnson on 29 per cent and Mr Hunt in the lead on 32 per cent.

Meanwhile, the neighbour who alerted police, and The Guardian, to the incident has defended his actions, saying political leaders must be “held accountable for all of their words, actions and behaviours”.

Tom Penn said he had recorded the altercation from within his own home after collecting a food delivery at his front door.

“After a loud scream and banging, followed by silence, I ran upstairs, and with my wife agreed that we should check on our neighbours,” he said.

“I knocked three times at their front door, but there was no response. I went back upstairs into my flat, and we agreed that we should call the police.

“The police arrived within five minutes. Our call was made anonymously and no names were given to the police. They subsequently called back to thank us for reporting, and to let us know that nobody was harmed.

“To be clear, the recordings were of the noise within my own home. My sole concern up until this point was the welfare and safety of our neighbours. I hope that anybody would have done the same thing.”