Just 76.7 per cent of A&E patients in Northern Ireland and only 81 per cent of admissions in Wales were seen within four hours in December, missing the target of 95 per cent.
The NHS in Wales has said last month was its busiest December for five years with 76,889 attending accident and emergency in that time.
In Northern Ireland just 76.7 per cent of accident and emergency patients were seen within four hours.
The latest figures show 89.8 per cent of accident and emergency patients in England were seen within four hours in the week ending 11 January, representing an improvement on the previous seven days when just 86.7 per cent attending units were seen in that time.
On average more than 4,000 hospital beds a day were occupied by patients whose discharge was delayed, the highest point this year and worse than at any point last winter.
The NHS 111 service took 255,000 calls for the week ending 11 January, down from 323,000 the previous week and a dramatic reduction from the peak of 439,000 for the week ending 28 December.
Dame Barbara Hakin, NHS England’s national director of commissioning operations, said: “Although we have seen a slight easing in the number of attendances and emergency admissions to A&E, the NHS continues to face unprecedented pressures on its frontline services – particularly A&E, NHS 111 and ambulance services.”
Wales’ Deputy Health Minister Vaughan Gething said: “Whilst different reporting mechanisms make it difficult to make direct comparisons with other parts of the UK, it is clear that all health services are experiencing significant pressures.”