Liam Payne's mum "hit [him] round the head" when she saw his raunchy Hugo Boss advertisement. Picture: AP

Liam Payne's mum "hit [him] round the head" when she saw his raunchy Hugo Boss advertisement.

The 'Stack It Up' singer stripped to his pants for the campaign and he admitted it's taken his mother, Karen Payne, some time to feel "comfortable" with the pictures.

He said: "My mum actually congratulated me in the end, but first off she hit me round the head when she first saw them. She wasn't comfortable with it at first but she's alright with it now."

The 26-year-old star recently had a surreal moment when he was confronted by a number of the adverts while out shopping.

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Speaking backstage at Hits Radio Live, he told he station: "I was walking down Oxford Street the other day and every single bus shelter was just me in my pants. I had like glasses on so I was trying to like Hannah Montana it out, like pretend I was wearing glasses but I wasn't."

While he's proud of the campaign, Liam admitted he needed to have a few drinks to bolster his courage before he posed for the photos.

He said: "The shoot itself was really good, the photographers I had are the best in the business. They took really good care of me and made sure that I was really comfortable with everything going on.

"Now, I had a few drinks before I went on... I was like, 'I need some courage to go on right now.' It's a lot to get naked in front of people."

Meanwhile, the former One Direction singer is looking forward to spending Christmas with his and former girlfriend Cheryl's two-year-old son Bear.

He said: "I just want to have a nice chilled day, spending a little bit of time with my son, watching him smile at presents and stuff."