A CHILDREN'S charity has reported a sharp increase in calls about child sex abuse to its helpline.

NSPCC Scotland said sexual abuse of children accounted for 13% of calls resulting in a referral in 2012/13 - or 133 cases - up nearly 70% up on the previous year.

It said the trend demonstrated a "clear need" for children to be given enough information to protect themselves from abuse at the earliest possible stage.

The rise comes as police are also reporting a rise in sexual offences against children under the age of 13, with more than 700 in 2012/13, an increase of 4% on the previous year.

Matt Forde, national head of service for NSPCC Scotland, said: "These figures are unfortunately just the tip of the iceberg.

"We know that it can take many years before victims disclose abuse and, in the meantime, there will be many more children in Scotland who do not understand what is happening to them, or who have tried to tell but have not been heard.

"Sexual abuse continues to be a terrible scar on our society which won't heal by itself. We have started to make inroads in giving children the protection they need, but there is obviously still a long way to go.

"Parents and carers can play an important role by ensuring their children are armed with the knowledge to recognise the wrong kind of behaviour and keep themselves safe."

Detective Chief Superintendent Gill Imery, Police Scotland lead for public protection, said: "A number of organisations including police, education, social work, health and numerous charitable organisations and other partners work in close co-operation and share information to identify children and young people who may be at risk.

"This multi-agency approach is crucial in tackling this particular issue. By doing this, agencies are able to discuss and share information to determine the most appropriate and effective action to protect and support children and young people who are, or may be, at risk."

NSPCC Scotland is re-running its Underwear Rule campaign, which encourages parents of children aged 5-11 to talk to them about staying safe from sexual abuse.

The campaign, originally launched last summer, aims to give parents the confidence to have an easy conversation about what is often seen as a difficult area of discussion.

Over 2.3 million people viewed an online video on the subject and nine out of 10 parents who were aware of the campaign said they now felt able to broach the subject though nearly half still haven't raised the issue with their children.

Gillian McGhee, from Clydebank, who has a five-year-old son, said: "It was a difficult subject to approach with my son, but using the Underwear Rule and the materials provided by the NSPCC gave me the confidence to start having these conversations with him.

"He responded really well to the materials."

The campaign complements the organisation's ChildLine Schools Service, which is visiting every primary school in Scotland advising children on how to stay safe from abuse.

A Scottish Government spokesman said: "All children and young people have the right to be cared for and protected from harm, and to grow up in a safe environment with their rights and needs are respected."