Figures released by the Prison Officers' Association show there were 1,176 assaults recorded across the region's 11 prisons between January and June this year.
The number was down from 1,997 assaults recorded in the same period in 2019 – a drop of 70 per cent.
The Association attributed this fall in assaults, in part, to gangs mixing less in order to reduce the spread of Covid-19.
But the charity Inquest warned this overlooks the harm done to inmates “languishing in conditions amounting to solitary confinement”.
HMPs Doncaster and Wetherby had the highest number of assaults recorded, with 283 and 214 respectively.
HMPs Wakefield and Full Sutton, which are both high security prisons and have housed notorious inmates over the years including the likes of Soham murderer Ian Huntley and serial killer Dennis Nilsen, recorded 47 and 18 assaults in this time.
Overall, there were between 100 and 113 assaults at prisons in Yorkshire which were classed as serious, including sexual assaults and attacks resulting in severe injuries.
The Ministry of Justice suppresses figures of serious assaults from prisons where there were fewer than five, meaning there is no exact figure.
Prisons across England and Wales recorded 11,800 assaults in the six months to June – thousands fewer than the 16,800 seen last year.
In March, prisons went into lockdown as the coronavirus spread, with many prisoners kept in their cells for 23 hours a day, visits from family and friends cancelled, and educational programmes suspended.
Restrictions were later eased, but POA national chairman Mark Fairhurst said that prisoners being allowed to socialise in smaller groups to reduce contact had been “a blessing in disguise”.
The union’s assistant general secretary Mick Pimblett said fewer prisoners being out of their cells at any one time meant gangs were mixing less, leading to less bullying and vulnerable prisoners feeling safer.
He added: “Not only have we kept prisoners relatively safe from Covid, violence has dramatically reduced.
“We must build on this success by ensuring that our prisons are adequately resourced, staff prisoner relationships continue to improve and we cater for the mental health of all who live and work in our prisons.”
Inquest, which campaigns on prisoner rights, said this ignored the potential damage to inmates kept under “indefinite lockdown”.
The group’s director Deborah Coles said: “Across the prison estate, men, women and children are languishing in conditions amounting to solitary confinement. The detrimental impact to physical and mental health cannot be underestimated.
“Extreme restrictions are being justified as the only way to contain the pandemic in prisons. This is not the case.
“To reduce ongoing harm we need to dramatically reduce the prison population. This is more important than ever to save lives.”
She added that resources must be reallocated so that no prisoner is released into “poverty or a lack of health and welfare support”.
A prison service spokesman said: “Assaults were falling before the pandemic following a concerted effort to drive down violence – including a £100 million investment in tough security measures.
“We introduced necessary restrictions on daily life, which have saved many lives during the pandemic, and these have been safely eased in line with the latest public health advice.”
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