Almost 600 social media accounts were shut down at the request of prison bosses last year, highlighting a “growing problem” of inmates using technology.

The number of social media accounts closed at the request of authorities almost quadrupled in three years, according to figures.

Officials intercepted material on platforms like Facebook, Instagram and YouTube – with more than 1,700 accounts removed from 2015 to 2018.

Cases were triggered by serving prisoners using illicit mobiles, or by content from inside jails being posted by people on the outside.

Some cases have highlighted the potential for images and footage to appear online, including the removal of accounts opened under the identity of Ipswich murderer Isaac Calver – pictured on Instagram in a jail cell during his trial with five others following the fatal stabbing of Tavis Spencer-Aitkens in June last year.

The Prison Officers Association warned the revelations risked undermining confidence in the justice system, while the Prison Service said it worked closely with social media companies to close accounts used by prisoners.

Ministry of Justice figures, released under freedom of information laws, showed removals increased from 153 in 2015 to 594 last year.

Glyn Travis, of the Prison Officers Association, said the rise highlighted “growing problems” and could undermine public confidence in the justice system, adding: “These sites continue to be accessed and prisoners are taunting victims, intimidating witnesses and organising criminal activity from the safety of a cell.”

Alex Mayes, of charity Victim Support, said victims “may feel unsafe knowing the perpetrator could potentially contact them or their family and friends”.

A Prison Service spokesman said: “We do not tolerate the use of mobile phones in our jails and we work closely with social media companies to close accounts being used by prisoners.

“We are investing millions in body scanners, phone-blocking technology and other measures to prevent phones being smuggled into and used in prison.

“Any prisoner found with a mobile phone faces extra time behind bars.”

YouTube said it had a dedicated process for police and the prison service to flag videos, and takes action when it finds threats or violations of its community guidelines.