Wait times at Peel Health Campus' (PHC) emergency department finished last year among the state's worst, the latest health data from 2018 reveals.
More than 33 per cent of patients arriving in the PHC emergency ward in December waited longer than four hours to be seen, according to the Department of Health monthly report.
This is the second longest ED wait time in the state, behind Joondalup Health Campus.
The “four-hour rule” requires 90 per cent of all ED patients be treated in less than four hours.
In November 2018, only 66.4 per cent of PHC emergency patients were seen in four hours or less.
Similarly, in December 2018, out of the 3821 people who attended the emergency department, 66.8 per cent were seen in four hours or less – down from 68 per cent in December 2017.
Examples of strain were on show at the facility during the Christmas period, with the Mandurah facility the only hospital across the metropolitan area to be put on ambulance diversion.
All patients picked up by St John Ambulance between 6pm and 10.30pm on Friday, December 28, who were deemed likely to require tertiary care or mental health care were taken directly to Rockingham General Hospital or Fiona Stanley Hospital.
PNC also started the year with the second-worst emergency waiting times at the beginning of 2018, behind Fiona Stanley Hospital.
Despite boasting improved wait times in May and June last year, patients who attended the Mandurah hospital's ED were gradually made to wait longer and longer as the year progressed.
The campus lags behind 23 state hospitals in meeting the four-hour rule and comes in well below the state average of 76.8 per cent of emergency patients being seen in four hours or less.
A South Metropolitan Health Service spokeswoman said the facility was "committed to providing timely access to care".
"A slight increase in ED wait times can be attributed to an influx of tourists and visitors over the summer period in the Peel region," she said.
"A number of initiatives have been introduced at PHC over the past year to improve ED performance.
"PHC continue to review its processes and the planned $5 million reconfiguration of [the] ED is expected to improve patient flow, have a positive impact on hospital wait times, enhance patient confidentiality and privacy, and improve overall patient comfort and satisfaction."
Australian Medical Association WA president Dr Omar Khorshid said an overcrowded ED was a symptom of "inadequate capacity within the entire hospital".
“For some time now, doctors have been reaching out to the AMA WA telling us of the strain on resources at the hospital," he said.
"The doctors and health staff at Peel Health Campus are doing the very best they can with limited resources.
“Patients deserve the same levels of efficiency and high quality of service across all hospitals in WA, not just at our tertiary facilities."
Without addressing the underlying problems at Peel Health Campus, patients will continue to suffer and face unnecessarily long waiting times for their care.Dr Omar Khorshid
Dr Khorshid said the recent $25 million cash injection from the federal government would "fail to resolve ongoing issues".
“Both state and federal governments need to work together to improve access to and delivery of health services, beyond just the emergency department of the hospital," he said.
“Without addressing the underlying problems at Peel Health Campus, patients will continue to suffer and face unnecessarily long waiting times for their care.”