Clip of Jacinda Ardern and Boris Johnson's 'violent' handshake goes viral

A clip of "the most violent handshake" as Prime Minister Jacinda Ardern met United Kingdom Prime Minister Boris Johnson has gone viral.

As Johnson welcomed Ardern outside his Downing St residence for the official photocall on Friday (local time), what is meant to be a symbolic greeting instead left some people feeling confused.

The rather energetic handshake lasted about five seconds and is coupled with what appears to be Johnson pulling Ardern's arm towards him.

As the pair smiled for the cameras, Johnson ignored questions about whether his "leadership was lacking", if he was "drowning in sleaze", and whether he'd take action over a politician facing groping allegations.

A clip of the handshake was posted to Twitter and sparked many jokes about whether Johnson had broken Ardern's arm given how vigorous it was.

"That is the most violent handshake I've ever seen," one person wrote.

"Someone call an ambulance, there's a woman at No. 10 that needs her right arm reattaching," another said.

"Jesus. Surprised her arm wasn't dislocated," a third wrote.

Other users joked that Ardern had to visit hospital so she could get her broken wrist attended to, while another questioned why Johnson was "being so weird with the hand-shaking".

One Twitter user compared Johnson's handshake with that of former United States President Donald Trump, who tended to pull recipients in close and try to dominate the greeting.

"It's Boris Johnson's attempt at the Trump power-yank. Says it all really (as if we didn't already know!)," they said.

When Ardern and Johnson met, they agreed to changes to the Youth Mobility Scheme, which currently allows people aged between 18 and 30 to live and work in the United Kingdom for up to two years. But the changes mean New Zealanders will be able to apply for the working visa up until the age of 35 and it will last for three years.

Also while in the United Kingdom, Ardern met privately with leaders, including British Labour leader Sir Keir Starmer and deputy leader Angela Rayner. She also met Prince William and had a phone call with Prince Charles.