More than 200 mobile phones or SIM cards were confiscated from prisoners at HMP Northumberland last year, a massive hike since the prison was formed seven years ago, a new investigation has revealed.
In 2011, the year when HMP Acklington and HMP Castington were merged to form what has become the 5th biggest prison in England and Wales, only 15 phones or SIMs were discovered, compared to 218 devices or cards in 2017, a 1,353% rise.
The number of confiscations per 100 prisons equated to 16.3 in 2017, compared to just 1.2 in 2011.
The management of HMP Northumberland passed from Her Majesty's Prison Service into the private hands of Sodexo Justice Services in December 2013. In its first full year of operation, 2014, 170 mobile phones or SIM cards were confiscated, or 12.8 per 100 prisoners. So there has been a 28% increase in discoveries since Sodexo took over.
An HMP Northumberland spokesman said: “Safety and security are our top priority, and these figures reflect the hard work of our staff in stopping illicit items getting into the prison and in detecting such items when they do.
“We continue to work closely with Northumbria Police to seek prosecutions for all those involved in the trafficking and possession of illicit items.
"Any member of the public who has information which would support us in our continual drive to stop these items getting in should either contact the prison directly or contact their local police office."
Nationally, at least 15,000 mobile phones or SIM cards were confiscated in English and Welsh prisons last year, equivalent to one for every six inmates.
Phones are used by some prisoners to order drugs and co-ordinate criminal activity inside and outside jail. A penal reform charity said the government had failed to tackle the root of the issue, whilehe Prison Service said improved security measures had led to more confiscations.
The BBC's Shared Data Unit compared figures for the period 2010-2014 and 2017 from ministers' answers to written questions in Parliament, Freedom of Information requests to prison services in Scotland and Northern Ireland and published prison population figures.
The analysis of official data found:
* The number of confiscations increased from 9,600 in 2014 to at least 15,000 last year, a 56% rise.
* In England and Wales, there was an increase from an average of nine discoveries per 100 prisoners in 2011, to at least 18 per 100 prisoners in 2017 (the equivalent of one in six);
* Prisons with the highest rates per 100 inmates were Ford, West Sussex (81); Aylesbury, Buckinghamshire (80); Hindley, Wigan (79); Buckley Hall, Rochdale (58) and Kirkham, Lancashire (57). HMP Northumberland had the 50th highest rate (16.3), out of 119 prisons.
* Prisons with the largest percentage rises in the rate of mobile phone handset and/or SIM card finds from 2011 to 2017 were Hindley, Wigan (10,350%); Doncaster (3,350%); Rochester, Kent (2,670%); Portland, Dorset (2,233%) and Risley, Warrington (1,541%). HMP Northumberland had the eighth highest rise out of 110 prisons.
* In contrast, the rate of discoveries in Scotland dropped from an average of six per 100 prisoners in 2012-13 to four per 100 prisoners in 2017-18;
* In Northern Ireland, the rate of discoveries has dropped from an average of 1.9 per 100 prisoners in Mar 2012 to 1.8 per 100 prisoners in 2017.
A former prison worker, who spoke to the BBC on condition of anonymity, said: "They [mobile phones] are a huge problem - they make getting any kind of contraband in very easy.
"They can sit all night with unlimited access to the internet and make voice calls. The big part of being in jail is you are cut off and denied your liberty. With the spread of mobile phones that's completely irrelevant.
"It's difficult to keep order in jail because staff are outnumbered. If prisoners don't take the authority seriously, it makes a joke out of the whole system.
"People see [videos posted on social media from inside jail] and they are less frightened of jail, they think their mates are having a whale of a time."
Mobile phones have been used by prisoners in recent years to orchestrate fatal revenge attacks, helped coordinate an armed, masked gang freeing a drug baron en route to court and by inmates flouting authority by broadcasting themselves live.
They are also associated with the spread of new synthetic drugs among inmates.
In January, London nightclub acid attacker Arthur Collins, ex-boyfriend of reality TV star Ferne McCann, had eight months added to his 20-year sentence for the attack for secreting a phone, two SIM cards and two memory sticks into jail inside a crutch.
"If prisoners had better access to phones, the massive trade in smuggling them in would stop and staff could concentrate on stopping the inflow of phones being used for crime," she said.
Private prisons had "led the way" by providing phones in cells with cheap providers where calls may be monitored and security risks managed, she added.
Peter Dawson, director of the Prison Reform Trust, said: "Knowing how many phones are seized is an important part of the story, but what's unclear is how many of the calls made on illegal mobiles in prisons are by people trying to stay in touch with their families.
"When a person can spend their entire week's prison wage in just 30 minutes on a prison phone, and has one hour a day when they can join the queue to do so, it's not surprising that the demand for illicit handsets is high."
The Prison Service said: "These statistics show that we are successfully stopping contraband from entering the prison estate.
"However, we acknowledge that more must be done and as Minister [Rory] Stewart has previously stated, there are only five ways in which contraband can be smuggled into prisons and we are taking steps to tackle all five.
"We've addressed flying contraband in by tackling drones, the throwing over of items by the use of nets and searches, the dragging in of items by identifying wires and the posting of drugs by photocopying letters.
"We are also taking decisive action to find and block mobile phones, including a £2million investment in detection equipment. We have legislated to stop phones from being used in prisons."