There are 98 patients at Cork University Hospital, waiting for admission to a bed, which is a record, according to the Irish Nurses and Midwives Organisation.
INMO Assistant Director of Industrial Relations for the Southern region Colm Porter said the number of patients being treated on trolleys, chairs and other inappropriate bed spaces in CUH was gravely concerning.
The union has put the overall level of overcrowding nationally at 641, with 444 waiting in emergency departments and 197 on wards elsewhere in hospitals.
The hospital worst affected by overcrowding is University Hospital Limerick, where there are 118 admitted patients waiting for a bed.
HSE figures put the number of patients waiting at Cork University Hospital lower at 59.
The HSE's national overcrowding figure is 444, with 313 patients on emergency department trolleys and 131 on ward trolleys.
