The High Court in Glasgow heard that 23-year-old Steven Davidson was looking after the baby girl while her mother, who had been up all night with the child, got some sleep.

Despite admitting he carried out the attack he has never given an explanation to either the child's mother or doctors or the police that would account for the injuries sustained.

But medical evidence shows that she was shaken and may have also been hit against something.

The child was is now two is unable to sit up or communicate and requires round-the-clock care.

The court heard that at 8am on October 13, 2012, the mother asked Davidson, of Dumbarton, to care for the baby, who was awake and crying and wriggling.

By 9.30am – just 90 minutes later – the baby was unresponsive and her eyes were closed.

Advocate depute Paul Kearney, prosecuting, said: “She was breathing, but seemed unconscious and did not respond to having her limbs moved or to her name.” The baby's mother, who had been roused from sleep by Davidson, noticed that her soft spot on her head felt firm and realising this was not normal phoned the emergency services.

Davidson admitted shaking the baby, throwing her against a surface to her severe injury, permanent impairment and to the danger of her life at a house in Dumbarton on October 3, 2012.

He was originally charged with attempted murder, but the Crown accepted his plea to a reduced charge.

The child was taken to the Royal Alexandra Hospital in Paisley and given a CT scan which showed bleeding inside her skull.

The next day she was transferred to the Royal Hospital for Sick Children in Glasgow.

Mr Kearney said: “A second CT scan was carried out there. This appeared to show the child had extensive damage to the brain caused by a lack of oxygen being supplied to the brain.” The child is cared for by her mother and other family members.

Mr Kearney added: “She has an acquired brain injury which has left her with a severe physical disability. She is not able to sit unaided, has restricted movement in her upper limbs.

“Although aged two she functions at the level of a child of four or five months.. She can make sounds, but cannot speak. She is described as an engaging child and can smile, laugh and cry and use facial expressions, but is otherwise unable to communicate, even though she clearly wants to.” “The child cannot take solid food and will need a wheelchair. She does however benefit from being cared for in a loving family environment.” Davidson told police that he had been suffering from toothache that morning when he was asked to look after the child.

He said she would not settle in her pram, but was fine sitting beside him in the living room in her bouncy seat as he watched television.

Davidson claimed that the child vomited at 8.45am and he changed her and put her in the pram to sleep..

He added that around 9.30am as he tried to wind her she would not wake up.

Mr Kearney told the court: “No mention was made of him having done anything to harm the child.” Judge Lady Scott deferred sentence on first offender Davidson until next month for background reports and allowed him bail.

Defence counsel Ronnie Renucci will give his plea in mitigation then.