Celebrities from supermodel Naomi Campbell to Hollywood actor Hugh Grant have been posting selfies of themselves when they wake up in bed in a new social media campaign, reported Daily Mail.

The aim is to raise money for and awareness of Unicef.

The celebrities use the hashtag #WakeUpCall #UNICEF Text SYRIA to 70007 to give £5 (S$10) or http://wwwwakeupcall.org.uk - with each person nominating three others to do the same.

Campbell, 44, was among the first to post her picture and judging from the picture, she puts on make-up first thing in the morning.

UK Unicef Ambassador for 13 years Jemima Khan, 40, posted a picture of herself with her mouth open. MailOnline said she launched the social media campaign to help Syrian refugee children, following a trip to Jordan's refugee camps.

MailOnline quoted her as saying: "The main aim is to raise lots of money fast for Syrian refugee children. I went to meet Syrian refugees in the camps in Jordan last week. There are currently 6.5 million Syrian children who are in desperate need of help."

She said she was inspired by the success of the Ice Bucket Challenge, which raised US$100m (S$127 million) for the Amyotrophic Lateral Sclerosis (ALS) Association and the No Make-Up selfie, which raised £8m (S$16 million) in six days for Cancer Research UK.

The Ice Bucket Challenge, which involves dumping a bucket of ice water on one's head to promote awareness of the disease and encourage donations, has been described as one of the most successful social media campaigns with CEOs, celebrities and sports stars getting involved.

Other celebrities who have supported WakeUpCall campaign include Ms Khan's ex-boyfriend and actor Hugh Grant, 54, and TV host and author Stephen Fry. Fry, 57, wrote in a caption: "I warn - look away now."

Superstar TV chef Nigella Lawson posted a picture of herself in bed with one hand shielding her face.

Money donated during the campaign will go to Unicef's Syria Emergency Fund.