HMP Ranby was described as "in crisis" by the Chief Inspector of Prisons Nick Hardwick after a critical report was released about the institution.
Following an unannounced 11-day inspection by HM Inspectorate of Prisons in March, the report found two prisoners died through "self-inflicted deaths" last year, and a further two have died in a similar way since then.
Conditions in part of the prison, which holds more than 1,000 men, were described as dirty and prisoners were found to have climbed netting in a bid to force a transfer to another facility.
Nearly half the population said they had felt unsafe having been victimised or intimidated, findings showed.
Evidence was also found of an increasing number of incidences of self-harm at the category C training prison, and the availability of legal highs was also found to have increased.
Chief Inspector of Prisons Nick Hardwick said the report showed a prison "in crisis".
More top news
A settled end to the weekend for many but a damp start to the working week
Liam Fox warned Brussels to put the prosperity of EU citizens ahead of any desire to make the UK pay a price for quitting the bloc.
A letter written a day before the Titanic sank by one of the disaster's victims has sold for a record-breaking £126,000 at auction.