PARENTS who fear their children have been abused by a paedophile nursery nurse have been urged by the police to come forward.

Alexander Mortimer, 28, was convicted yesterday of carrying out the abuse of two young children who were enrolled at the South Lanarkshire Council-run nursery where he worked.

He admitted at the High Court in Glasgow to abusing his victims, aged two and four, and possessing 18,000 images of child pornography, many among the "most depraved" seen by detectives.

The paedophile is also known to have trawled through Facebook offering to babysit for children at the nursery where he worked, which cannot be named for legal reasons, since 2008.

Police are satisfied all of his victims have been identified, but have asked anyone with further information on Mortimer's background to contact them.

Mortimer, of Rutherglen, South Lanarkshire, had also asked the council about becoming an adoptive or foster parent.

He came into contact with his victims through their grandmother, who was a colleague at the nursery. He offered to help care for her daughter's two sons but went on to abuse them during shopping trips and at a funfair at Strathclyde Country Park.

The extent of the abuse emerged when police received intelligence on his hoard of child pornography and found videos and images of a faceless man sexually assaulting the two boys.

Forensic analysis of Mortimer's hands, including scarring and a mole, showed he was the man in the shots.

Detective Chief Inspector David Marshall, of Strathclyde Police, spoke of the agony endured by parents of children at the nursery, with many mothers removing their children when news of the investigation broke.

He said: "Mortimer consistently refused to co-operate with police, prolonging the agony for the families involved.

"We understand the anxieties of the families who have children at the nurseries and also the wider community but I would like to reassure them we are satisfied we have captured and acted on all the available evidence.

"However, we would ask anyone with further information about Mortimer to get in touch.

"We are grateful for the co-operation of the families in what was a very harrowing time for them. We hope Mortimer's eventual admission of guilt will assist them in some way during the long and difficult process of dealing with the effects of such despicable crimes."

Mortimer's Facebook activities were also investigated, but no action was taken in this regard.

Mortimer admitted to the five charges relating to child abuse and pornography, which were committed between January 2009 and January this year.

Prosecutor Alison Di Rollo told how Mortimer had offered to help look after his colleague's grandchildren after hearing how their mother was having difficulty in coping with their care.

Miss Di Rollo said the grandmother assured her daughter there would be "no problem". Both now felt "very, angry and guilty" over the abuse.

In April last year, he began occasionally taking the children out on their own and soon after started taking indecent photos of the youngest of the pair.

The court heard how Mortimer sexually assaulted one of the children on a number of occasions, filming and photographing the abuse. He carried out a similar attack on the older youngster.

In January, computer equipment was seized and 17,967 indecent images and 582 film clips were found at the home he shared with his parents and sisters.

Mortimer said he had once carried out college work into child abuse, and may have "inadvertently" accessed certain sites. Miss Di Rollo asked the court for a risk assessment to be carried out, which could lead to an Order for Lifelong Restriction.