The number of patients who waited longer than 12 hours in A&E to be treated has more than doubled, new figures have revealed.
Within a three-month period, the number of people waiting for treatment in hospitals in Northern Ireland for more than half a day jumped from 77 in October to 168 in December.
Overall, 311 people were waiting more than 12 hours during that period – breaching the health minister's targets. The ministerial goal, set by Edwin Poots, is to have 95% of patients treated in A&E within four hours and no one to wait more than 12 hours.
Despite the spike, both the Department of Health and the Health and Social Care Board (HSCB) say that compared to the same period in 2012, the figures actually show a reduction in 12-hour waiting times.
The statistics released by the Department of Health also noted the performance "declined" at the Royal Victoria Hospital with the number of people waiting more than 12 hours jumping from 21 in October to 79 in December.
This was before the Major Incident declared at the RVH in January.
For several hours, the A&E unit was at "breaking point" with the trust being forced to call in emergency staff to cope with the level of patients.
MLA and Health Committee member Kieran McCarthy said the figures are another clear indication of serious problems with the infrastructure of the Health Service.
"This is a clear sign that the A&E departments are under severe stress and are not hitting the targets," he said.
However, the figures do show the number of patients who waited longer than 12 hours decreased by 71% from 579 in December 2012 to 168 in December 2013.
At the Ulster Hospital it dropped significantly from 286 to 21.
A statement from the Health Board said from October to December 2013, there were 326 breaches of the 12-hour standard.
"This represents a reduction of 950 (74%) compared to the 1,276 breaches during October – December 31, 2012," the spokeswoman said.
A spokesman for the department said: "In December 2013, 99.7% of 55,059 patients were assessed, treated and either admitted or discharged within 12 hours.
"The increase in 12-hour breaches since October can be attributed to seasonal factors associated with winter conditions.
"When compared to December 2012, the number of 12-hour breaches has fallen significantly from 579 to 168."
A spokeswoman for the Belfast Trust said it has seen an increase in attendances for the months October, November and December 2013 in comparison with the same time frame last year, but said it is "striving" to improve waiting times.
They said a number of improvements have already been made and others are in progress.
This has included two emergency department nurses who will undertake training as Advanced Nurse Practitioners.
"We do not want anyone to have to wait long for treatment and our staff continue to work extremely hard to see patients as quickly as they can.
"All patients are seen and triaged when they arrive in ED.
"Anyone requiring emergency treatment is always seen immediately," the spokeswoman said.