One Direction star Harry Styles kisses James Corden on festive Carpool Karaoke

One Direction fans have descended into hitherto unexplored levels of hysteria – after Harry Styles kissed Late Late Show host James Corden.

The singer locked lips with Corden on a special festive edition of the Late Late Show’s Carpool Karaoke.

In the clip, ‘Santa Claus is Coming to Town’ is playing as Corden tells the singer, “Happy Christmas, Harold!”

The singer then leans in for a snog, kissing Corden on the lips.

Corden adds: “I did not expect that at Christmas!”

The kiss was celebrated by fans of the singer on Twitter, who went into overdrive when the clip was released.

The pair have kissed at least once before, smooching him on Sky panel show A League Of Their Own.

Styles has made his recent tour a celebration of equality.

He told the crowd at one show: “If you are black, if you are white, if you are gay, if you are straight, if you are transgender – whoever you are, whoever you want to be, I support you.

“I love every single one of you.”

The ex-1D singer recently kicked off the first leg of his worldwide solo tour, following the release of his first album earlier this year.

During many of the concerts the singer has waved a rainbow flag, draping it over his mic stand and featuring it prominently onstage.

But at his show at Washington DC’s DAR Constitution Hall, Styles made a even more charged gesture.

In the shadow of the White House, the singer was thrown a transgender pride flag by a member of the audience.

Styles waved the flag on-stage – alongside an Puerto Rican flag.

The symbology was not lost on the crowd, given President Trump’s much-criticised stances on Puerto Rico and transgender issues.

Earlier this year, the global megastar opened up about his sexuality.

He said: “It’s weird for me – everyone should just be who they want to be.

“It’s tough to justify somebody having to answer to someone else about stuff like that.”

LOS ANGELES, CA - OCTOBER 21: Harry Styles performs onstage at CBS RADIO's We Can Survive 2017 at The Hollywood Bowl on October 21, 2017 in Los Angeles, California. (Photo by Kevin Winter/Getty Images for CBS RADIO)

He praised Wrecking Ball singer Miley Cyrus for coming out as pansexual, saying: “Being in a creative field, it’s important to be progressive. People doing stuff like that is great.”

But Styles said he would not be joining her in defining his sexuality.

Asked if he has ever labelled himself, he said: “No, I’ve never felt the need to really. No.

“I don’t feel like it’s something I’ve ever felt like I have to explain about myself.”

Before the band’s break-up, there were tensions inside One Direction when fans persistently theorised that Styles was in a relationship with fellow singer Louis Tomlinson.

Tomlinson recently addressed the rumours, saying they are “disrespectful” to his girlfriend.

He told the Sun: “It kind of happened naturally for me and Harry because a certain amount of the fans drew up this conspiracy. When it first came around I was with Eleanor, and it actually felt a little bit disrespectful to [her].

“I’m so protective over things like that, about the people I love. So it created this atmosphere between the two of us where everyone was looking into everything we did.

“It took away the vibe you get off anyone. It made everything a little bit more unapproachable. I think [what’s happened since] shows that it was never anything ‘real’ if I can use that word.”

Ex-bandmate Liam Payne previously admitted the gay relationship rumours drove him “insane”.

Styles has long been an enthusiastic advocate for the LGBT community.

In 2014, he showed his support for out NFL star Michael Sam while performing at a One Direction concert, by wearing the American football player’s St Louis Rams jersey.

Earlier this year, he said on French TV that LGBT rights were fundamental, not political.

“Stuff like equality feels much more fundamental,” he said. “I feel like everyone is equal.

“That doesn’t feel like politics to me.”