Nearly of fifth of patients in the Anglia region are waiting longer than four hours to finish treatment in major hospital Accident & Emergency units.
In the worst-performing hospitals, the figure rises to one third of patients with long waits.
The latest figures from NHS England show that more than 176,000 people attended casualty departments in the region's major hospitals in December 2017 - a rise of 4,500 compared with November.
A total of 33,000 patients faced a wait for more than four hours before they were discharged after treatment or admitted to hospital. That was 19% of the total.
Nationally waiting time targets in Accident and Emergency departments have hit their lowest level in 14 years.
Official figures released show the NHS ended the year with the same A&E waiting time performance level in December - 85.1% - as at the start of the year, equalling January's record low and the worst result since the target was introduced in 2004.
Staff have been faced with rising numbers of flu cases and respiratory illness, with 48 flu-related deaths in England so far this winter.
The best performing hospital in the Anglia region was the Luton & Dunstable University hospital with 98% of patients in A&E either discharged or admitted with the four hour target.
The poorest performing hospital was the Princess Alexandra in Harlow where 67% of patients finished emergency treatment within four hours.
Percentage of patients finishing treatment within four hours in A&E units in hospitals in the Anglia region (Dec 2017)
The NHS target for the number of people treated within four hours in A&E is 95%. The figure in December 2017 was 85%.
- Basildon & Thurrock - 83.6%
- Bedford - 85.5%
- Cambridge (Addenbrooke's) - 83.4%
- Colchester - 88.5%
- East & North Hertfordshire (Lister, Stevenage) - 77.2%
- Ipswich - 86.2%
- James Paget, Gorleston - 83.1%
- Kettering - 73.4%
- Luton & Dunstable - 98.1%
- Mid Essex (Broomfield, Chelmsford) - 74.2%
- Milton Keynes - 87.7%
- Norfolk & Norwich - 69.0%
- Northampton - 83.2%
- NW Anglia (Peterborough, Stamford, Hinchingbrooke) - 68.1%
- Princess Alexandra, Harlow - 67.3%
- Queen Elizabeth Hospital, King's Lynn - 81.0%
- Southend - 76.7%
- West Suffolk, Bury St Edmunds - 83.3%