Some 343,412 people around the country are waiting for an outpatient appointment, it has been revealed.
The number of people spending 12 months on a waiting list has grown from 4,937 at the end of last year, to 28,185 in May.
The figures are contained in the HSE's Performance Assurance Report for May, which also showed a €162m budget deficit in the five months to the end of May.