Newsnight host Jeremy Paxman has been accused of being “pathetic” and “bizarre” after an interview with London Mayor Boris Johnson descended in to giggles and “playground” questioning.

Paxman began the interview with the Conservative mayor on Tuesday night's programme discussing issues such as the London riots, the 50p tax rate and how poverty and deprivation could be tackled.

But it didn’t take long before Paxman appeared to lose his way. He suddenly seemed more interested in examining his finger nails, laughing and generally giving Johnson something he rarely does with his subjects – an easy go.

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He let Boris become over-familiar by touching his suit jacket so he could get his points across. At one point Johnson seemed to ignore Paxman and instead talk directly into the camera.

At one point a debate started about whether a camera being used to film the interview was broken or not. “There are parts on the underside of that camera that are damaged,” said Johnson getting up to examine it.

“Britain is scuffed, is that what you are saying?” asked Paxman.

After a short moment to discuss tax issues the pair moved on to David Cameron and rumours that Johnson and he don’t see eye to eye.

“What’s the difference between you and David Cameron?” asked Paxman.

“Well, I’m the Mayor of London and he’s the Prime Minister. I’m older than him, I’m considerably heavier, what else? I beat him at tennis the other day.”

By this time both men were laughing and rocking in their chairs. When Paxman moved on to the thorny issue of a possible difference of opinion between Johnson and Cameron Johnson huffed and the camera and looked around the studio.

“This is really good. When do you stop beating your wife questions. You cooked this one up carefully. What I want to talk about on your show, Jeremy is, I want to talk about the things that matter to me.

“I’m sufficiently versed in the ways of the media and indeed your brilliant interview technique to know that if I talk about the differences between me and Cameron, whatever they may be, all the things I want to say, things I’ve been saying in that hall about what we are doing for London, will be completely obscured in some kind of Tory split story.”

At its most bizarre moment Paxman grilled Johnson about leading the Tory party, but Boris managed to turn it on to Paxman saying he should stand and Boris would be the campaign manager.

“You’ve got the gravitas, you’ve got the name recognition, everybody knows that you’re probably quite Conservative, even though you sort of levitate over party policy.

“I think you’d be an ideal candidate. What about it? Down the line Dave’s eventually going to pack it in, and … and…”

“Have you finished?” said Paxman smiling at Johnson’s diversion.

“Look, it’s an offer.”

“We’ll it’s very generous but I’m going to be declining it.” At the end of the interview, when being asked about tension with Cameron, Johnson said: “This is playground stuff.”

“You are quite right, it is," agreed Paxman.

Twitter erupted with reaction over the interview. Labour’s Harriet Harman said: “Pathetic interview by paxman of Tory Johnson. What about real issues for Londoners?”

Sky News presenter Glen O’Glaza tweeted: “Agree bizarre, but rarely see TV like that: Paxo-Boris hilarious and quite mad, & women steamrollered hapless Paxman.”

While the Guardian’s Polly Toynbee wrote: “Why Paxman so cosy/giggly/friendly w Boris? Has he lost his teeth?”

A BBC spokesperson said: "As regular Newsnight viewers will know a meeting between Boris and Jeremy takes on a life of its own.

"Both have unique styles which makes for an engaging if not traditional interview and last night's encounter received a strong response from our audience - much of it positive."