Pressure on accident and emergency departments has seen a large increase in the number of hospital trusts reporting patients waiting more than 12 hours to be admitted, an HSJ analysis has found.

Department of Health and NHS England figures show a greater number of trusts having to delay the admission of emergency patients by 12 hours or more after clinicians have decided to admit them.

Figures for 2012-13 show 167 emergency patients waited more than 12 hours compared with 123 in 2011-12.

In the first two weeks of 2013-14 alone, meanwhile, a dozen trusts have together reported a total of 40 waits of more than 12 hours.

The trusts which performed worst in recent weeks blamed a mixture of bad weather, an increase in the seriousness – or acuity – of patients’ condition, and problems caused by the deployment of urgent care phone service NHS 111.

The long waits are sometimes referred to as “12 hour trolley waits” and have generally been considered to be a rare and serious occurrence in NHS hospitals.

Data for 2012-13 and 2011-12 shows a handful of trusts were responsible for the bulk of the long waiters. However, HSJ’s analysis shows an increasing number of trusts reporting breaching 12 hours.

Between April 2011 and the end of March 2013, 36 trusts in England had seen at least one instance of a patient waiting more than 12 hours.

A further six organisations on top of these 36 recorded one for the first time in the first two weeks of 2013-14.

The news comes as many hospitals declare “major incidents” as they struggle to cope with increasing emergency admissions.

East Kent Hospitals Foundation Trust and Shrewsbury and Telford Hospitals Trust declared “major incidents” earlier this month.

Shrewsbury and Telford has seen 32 12-hour breaches since the start of January. Only Brighton and Sussex University Hospitals Trust recorded more – with 52 in the same period.

One hospital chief executive told HSJ the winter had been the most severe in 10 years, and lasted for longer than normal.

Another hospital chief executive said: “If we hadn’t opened extra beds I don’t know how we would have got through this winter.”

She added that her trust had seen a large increase in patients over 80, who were more acutely ill.

She said: “These were absolutely appropriate admissions. The problem is discharging them to social care is more difficult [because of delays caused by making sure they had appropriate facilities and support plans outside hospital], so they take up a disproportionate amount of bed days.”

HSJ understands a number of hospital chief executives are considering calling “risk summits“ – a type of local system-wide meeting designed by the Department of Health to highlight threats to service quality – to address the inability of their organisations to deal with sustained increases in demand.

Senior sources told HSJ there were thought to be particular problems in the south of England.

Meanwhile, NHS Interim Management and Support told HSJ its Emergency Care Intensive Support Team was busier than ever in the past. Intensive support teams are currently working with 64 trusts, compared to a monthly average of 57 in 2012.

Health sector regulator Monitor’s April bulletin to providers said it expected to see a significant number of hospital trusts fail to meet the target of admitting or discharging 95 per cent of A&E attendees within four hours of arrival during the final four months of 2012-13.

Figures for the third quarter of the year showed 32 foundation trusts missing this target, up from 14 in the same period in 2011-12.