Monthly figures for June 2014, published today, show a sharp rise of 22.5% in delayed transfers of care in Welsh hospitals.
41% of patients experiencing bed-blocking were aged 85 or over.
49% of patients waiting to leave hospital had been delayed for three weeks or more.
Darren Millar AM, Shadow Minister for Health and Social Services, said: “Bed-blocking is at the heart of the capacity problems currently facing the Welsh NHS.
“It is vital for both the wellbeing of individual patients and the efficient delivery of healthcare services that patients are treated in the most appropriate surroundings.
“These figures show a worryingly sharp rise in incidents of bed-blocking in Welsh hospitals, which is distressing for the mostly elderly patients affected and which denies beds for those who need them.
“After 15 years in charge of running the Welsh NHS, Labour Ministers have failed to get to grips with the problem of bed-blocking.
“Labour’s legacy of record-breaking cuts to the Welsh NHS budget, the axing of a fifth of all NHS beds under Labour and inaction over bed-blocking, all contribute to a capacity crisis in the Welsh NHS.
“Labour Ministers must address bed-blocking in Welsh hospitals, which remains a major logjam in the health service and which appears to be getting worse.”