Around 360 hospital appointments are wasted every day in Northern Ireland — because the patient never turns up.
More than 130,000 slots were missed across the five health trusts in a single year.
DUP MP Carla Lockhart, who obtained the details, said it was a “startling” waste of time and resources.
She said it was time to start penalising repeat offenders.
The figures, released by Health Minister Robin Swann, show the problem is on the rise.
The number of new and review outpatient appointments which the patient did not attend without notice increased from 126,393 in 2016/17 to 132,288 in 2018/19.
Ms Lockhart said that the statistics are "startling".
“In 2018/19, 132,288 appointments have been lost across Northern Ireland because of people failing to turn up and failing to notify the hospital they would not attend. That represents around 360 appointments per day where our healthcare workers are not being fully utilised. Time and resources are being wasted.”
The latest Department of Health figures show a rise in people waiting for appointments.
As of March 31, 307,066 patients were waiting for a first consultant-led outpatient appointment — 6.3% (18,312) more than the same point in 2019.
Almost four fifths (79.1%, 242,864) were waiting more than nine weeks, compared with 74% (213,708) the previous year.
Nearly two fifths (38.1%, 117,066) were waiting more than a year, compared with 33.9% (97,851) at the same point 12 months earlier.
Ms Lockhart added: “The last few months has highlighted just how invaluable our health service is.
“The pressures on the system posed by Covid-19 have been withstood heroically, but now we look to contain Covid-19 while also re-opening our health service.
“We need to tackle waiting lists and restart much needed treatments across the system.
“If we are to do that as efficiently and as effectively as possible, we need to public to respect our health service and medical staff, by attending appointments or having the courtesy to get in touch if attendance is not possible.
“Others can then take that place and the backlog of treatments worked through more quickly.
“We cannot continue with this wasting of time and invaluable resources. I really do urge the public to play their part in the health services restart.
“If this increasing trend continues, other penalties will have to be explored for repeat offenders.”