Plaid Cymru says A&E waiting times not acceptable
Performance at Welsh A&E departments in December was worse than the same time last year, official figures show.
This is despite Welsh Government assurances the NHS has been coping better this winter.
In December, 77.8% of patients spent less than four hours in A&E before being admitted, transferred or discharged. This is compared with 79% in the same month in 2017.
The target is 95% should be seen within four hours.
Plaid Cymru's health spokeswoman Helen Mary Jones said staff were "working their socks off" but there needed to be a proper look at the whole system.
Meanwhile, NHS Wales chief executive Dr Andrew Goodall said waiting times in north Wales were skewing the picture for the health service as a while.