The president of the Prison Governors Association has warned prisons across England and Wales are under a “toxic mix” of pressures following a disturbance at HMP The Mount.

Andrea Albutt launched a blistering attack on the Ministry of Justice (MoJ), after prisoners armed with weapons took over a wing at the Hertfordshire Category C male prison in Bovingdon for two days.

In an open letter published as riot officers were called to a prison for a second day to resolve the issue at 5pm yesterday, the governor said a recent increase in indiscipline among inmates was "of grave concern".

The Government has said it has taken "immediate action" to increase prison officer numbers while creating a new body to drive through its reform programme.

However Ms Albutt said members had told her that they have seen "nothing tangible" come from the MoJ to ease the burden on prisons, leaving governors facing "unacceptable stress and anxiety" on a daily basis.

She said: "We know many prisons are in crisis and I deliberately use that term, because it can't be dressed up in any other way."

The governor warned that an unforeseen rise in prisoner numbers had left the estate with "virtually no headroom" in spaces, while seasonal pressures were adding strain to limited staffing levels.

A spokesman for the MoJ said: "We know that our prisons have faced a number of long-standing challenges, which is why we have taken immediate action to boost prison officer numbers and have created Her Majesty's Prison and Probation Service.

"This will help to create a distinct, professionalised frontline service and will ensure that policy and operations are working closely together to deliver these much needed reforms.

"We need to create calm and ordered environments to help ensure effective rehabilitation, and we continue to work closely with the unions and all staff to help achieve these vital reforms and make prisons places of safety and reform."