Gigi Hadid stars in Zayn Malik's music video because they were both "uncomfortable" with him getting close to anyone else.

Zayn Malik and Gigi Hadid

Zayn Malik and Gigi Hadid

The 20-year-old model made a surprise appearance in the promo for her boyfriend's debut solo single 'Pillowtalk' and insiders say the couple were keen to "celebrate" their relationship publicly.

A source told Britain's Grazia magazine: "They obviously both knew the video would be a huge talking point.

"The truth is, it was important for Zayn that Gigi be featured.

"The song needed a sexy video, and even if it is still early days, neither felt comfortable with the idea of him filming those intimate scenes with anyone else.

"They're both excited about the relationship and wanted to celebrate it."

Gigi and Zayn share a kiss in the video, while another scene sees the model posing for the camera as what appears to be blood rolls down her cheeks.

The 23-year-old singer previously teased fans that it was pretty "black and white" that his single would address the topic of sex.

He said: "I think I'm pretty black and white about what it's about. Everybody has sex, and it's something people want to hear about. It's part of everybody's life, a very big part of life! And you don't want to sweep it under the carpet. It has to be talked about."