The 16-year-old boy was thought to have been waiting on a taxi with friends on Faifley Road when the attack took place in the early hours of the morning.

Police said a man approached the boys and started speaking to them before slashing one on the face and walking off.

After being treated at the Western Infirmary the boy was transferred to the Southern General hospital, where he needed a number of stitches.

Police said the suspect is thought to be around 30-years-old, white, of stocky build and approximately 6 ft tall.

He was wearing a dark-coloured Stone Island hooded jacket and had a Rangers scarf around his face.

Detective Constable Clare Moran, at Clydebank CID, said: “This was a horrific attack on a young boy which has left him with permanent facial scarring. "From what we believe, it was completely unprovoked, neither the victim nor his friends knew the assailant. I am appalled that someone would do this then casually walk off.

“It is important that we trace this individual and I would appeal to anyone who was in the area or recognises the distinct description to come forward.” Anyone with information is asked to telephone the CID at Clydebank on the non emergency number 101. Alternatively they can telephone Crimestoppers on 0800 555 111 where anonymity can be maintained.