CRIMINALS are using children's chocolate treats to smuggle drugs over a prison wall to ­inmates.

Kinder Surprise eggs are being thrown over the prison wall at Barlinnie Prison in Riddrie, claims a source.

It is understood the drugs are hidden in yellow plastic capsules, normally used to store toys inside the eggs.

A source close to the prison said: "Drugs are being stored inside the Kinder Surprise eggs and then thrown over the prison wall.

"They are usually thrown over at 'exercise time' when an inmate is out in the yard to collect it. The switch time and place is organised through contraband mobile phones."

The number of drugs seizures in the jail have risen by 176% in the last three years. So far this year, prison staff have intercepted 127 drug-smuggling attempts.

Sniffer dogs and intelligence gathering operations are being used to combat the problem, officials say.

Drugs expert and Labour MSP Graeme Pearson said: "Prison officials at Barlinnie will be well used to this kind of practice.

"However, they now have to deal with the additional problem of access to the ­internet and mobile phones.

"This allows a more co-ordinated approach."

A Scottish Prison Service spokeswoman said: "We ­invest heavily in resources, development of intelligence and working with partner agencies to address the problem of illicit articles being introduced into our prisons.

"Any information brought to our attention is always assessed."