Overcrowding at a Vancouver Island prison is to blame for a vicious attack against one of its guards Tuesday afternoon, according to the union that represents staff at the facility.

The guard at the Vancouver Island Regional Correctional Centre (VIRCC) underwent surgery late last night for a broken ankle and is recovering in hospital. He received injuries to his feet and knees, as well as multiple lacerations, after being attacked by a segregated prisoner at the institution around 3 p.m.

Dean Purdy of the B.C. Government Employees Union says although the facility was originally designed to hold just over 200 inmates it now holds almost 370 -- and crowding is leading to problems.

"When you increase the amount of inmates that increases the potential for violence and promotes a mob-like mentality," he told ctvbc.ca.

"Coupled with newer staff and staff turnover that's a recipe for disaster."

Purdy, who has worked at the institution for 22 years, says there have been 63 attacks against staff since 2003, the year the province closed nine institutions and laid off hundreds of corrections workers in British Columbia.

"Prior to 2003 you could count the amount of attacks on one hand. But when they lifted the cap for the rule of 20 inmates to one staff member it all changed."

Purdy says ratios have jumped to as high as 60 to one in recent years at some facilities.

The VIRCC was opened in 1913 and was rebuilt in the 1980s. It functions as a remand and sentenced facility for "inmates of all levels of risk."