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New technology is to be used to block mobile phones that have been smuggled into prison, even if the authorities are unable to find the device.

The Scottish Prison Service (SPS) has been trialling techniques that can detect phones from their mobile signal.

They are then able to block the phone, and seek a court order to completely remove the device from the network.

This effectively makes the device useless, even if a different sim card is inserted into it,

MSPs on the Scottish Parliament's justice committee have now approved the technology for use, after Justice Secretary Michael Matheson offered assurances that it was unlikely to interfere with mobile phones being used by people living close to prisons.

Mobile phone use has become a major problem in prisons, with inmates using them to plan escapes or indiscipline, intimidate witnesses or to continue organising drug dealing or violence while they are behind bars.

So far this year, 285 handsets and 116 sim cards have been recovered in Scottish prisons, and 76 prisoners have been charged with possession of a mobile phone.

It was reported last month that prisoners at Saughton Prison in Edinburgh had posted nude photographs of themselves on social media.

With mobile phones the size of matchboxes available, it is difficult to prevent devices and sim cards being smuggled in - and for prison officers to find those that are already in circulation.

The SPS has been trialling "IMSI catcher" technology at two Scottish jails - HMP Shotts in North Lanarkshire and HMP Glenochil near Alloa - which intercepts signals inside the prison by mimicking a mobile phone tower.

Once the signal has been detected, the authorities are able to match it to an individual device, which can then be completely blocked by the mobile networks.

Mr Matheson told the committee that the illegal use of mobile phones in prisons presented a "serious risk to the security of prisons, and to the safety of the public".

He added: "These regulations will not prevent the introduction of illicit mobile phones or their component parts to prisons.

"However the successful disabling of a mobile phone will put it beyond use and will seriously disrupt the activities of those individuals, including those involved in serious and organised crime who would seek to extend their criminal activity, threats or presence beyond the walls of our prisons."