Officers 'pushed down stairs' at HMP Berwyn, Wrexham
Prison officers have gathered outside HMP Berwyn in Wrexham following claims of a "series of assaults" on staff at the UK's biggest prison.
Alleged incidents have included staff being pushed down stairs and spat on.
The Prison Officers' Association (POA) also claimed the inmates have not faced any punishment, and a confidence vote went against senior managers at the category C prison last week.
A Prison Service spokesman said violence would not be tolerated.
Up to 50 prison staff gathered at the gate of Berwyn to be addressed by POA national chairman Mark Fairhurst.
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"Over the course of the last four weeks there's been quite a few assaults on staff and the staff have highlighted to me their concerns about the lack of consequences for those actions," he said.
"We want safe working conditions and I'm pleased to say the committee are engaging with the management, we're trying to resolve those issues.
"Last weekend we had a member of staff butted and lost some teeth, we've had 'pottings' where prisoners throw excrement and urine over staff and I've heard that over the weekend a member of staff was kicked down the stairs."
'Strongest possible punishment'
Mr Fairhurst said attacks on staff were not unusual in prisons but in Berwyn they were trying to promote a rehabilitation culture which prisoners needed to buy into.
He added: "If they are going around assaulting staff, they need to be transferred out of Berwyn immediately and put into the mainstream because they're not engaging with the ethos we're trying to create at Berwyn.
"Unfortunately that's not happening and it's having a massive effect on staff morale and staff safety."
A Prison Service spokesman said: "Violence against our hardworking staff will never be tolerated and when incidents occur we push for the strongest possible punishment.
"In the last week alone two prisoners were sentenced to additional time behind bars for breaking prison rules."