A paedophile raped a 14-month-old baby girl in what a judge described as an "unspeakable act of depravity".

David Morrison, from Grangemouth, took photos of the sex attack on the child before distributing them on the internet.

The 45-year-old was placed on a lifelong restriction order at the High Court in Edinburgh on Monday after admitting to raping the baby.

Lord Bonomy told Morrison: "You have committed unspeakable and incomprehensible acts of depravity towards a child and even invited like-minded paedophiles to share your experience by photographing and transmitting the evidence."

He added that he was obsessed with himself and had indulged his "own deviant fantasies".

A police investigation launched into Morrison has led to 15 other paedophiles in the UK being caught and a further 75 worldwide in 24 countries, including the USA, Canada and Sweden.

Detective Chief Inspector Barry Blair of Central Scotland Police public protection unit said: "I think it is important to realise David Morrison is clearly one of the most dangerous sexual predators we have had to investigate and we think that is reflected in the sentence today.

"We are pleased he will remain behind bars until he is deemed to be no longer a threat to the public. It took a lot of work. It took a lot of resources, but we have got a result today and that makes it worthwhile.

"It really was quite an intricate investigation in terms of pulling together the strands of evidence to show David Morrison really was the person responsible for it, culminating in the veins on the back of his hand which we were able to show to an expert."

Morrison, formerly of Kersiebank Avenue, will serve a minimum of four years in prison before he is eligible to apply for parole.

During the investigation, Professor Sue Black, from Dundee University, was able to link an image recovered from a computer to Morrison through the veins on his hand.

The paedophile was found to have amassed a total of 13,141 still images and 166 videos of child pornography on his computer seized in December 10, 2010.

Defence counsel Derick Nelson told the court that a report on Morrison revealed he was suffering from "several personality disorders" and was assessed as falling into the category of high risk. He added: "He realises he still does need help."

Morrison earlier admitted abusing and raping the child at a house in Grangemouth and possessing and distributing indecent photos of children in 2009 and 2010.

Lord Bonomy told Morrison: "I recognise that you were subjected to abuse, both mental and physical, in your early years which were spent in very deprived circumstances."

He said flaws in the sex attacker's character had been allowed to blossom resulting in a history of irresponsibility and criminal behaviour. Morrison was placed on the sex offenders register.