Trusts are facing a difficult six weeks before the promised right for patients to be treated within 18 weeks comes into force on 1 April, at the likely start of a general election campaign.

Operations cancelled during the severe weather and outbreaks of norovirus, together with the need to clear backlogs of patients who have already waited more than 18 weeks, mean many trusts could struggle to meet the target of treating 90 per cent of inpatients within 18 weeks of referral.

Some trusts had to deal with massive increases in emergency cases

Strategic health authorities are assessing the impact on their areas but board papers from the end of January show there were already concerns about the ability of some trusts to hit the 90 per cent target.

Some areas saw achievement figures dip as they tried to treat long waiters first.

NHS South East Coast says the weather increased the risk that some organisations could fail to meet the standard. It had identified six trusts with “material backlogs” which might not clear them by April.

A spokesperson said: “We are in the process of quantifying the nature and extent of the elective operating capacity that was lost during January, and we will be working hard with trusts across the region to get the best possible progress towards meeting the 18 week target.”

In the East of England, five trusts are in danger of not clearing their backlogs by the end of March, although the snow had relatively little impact.

In the East Midlands, United Lincolnshire Hospitals Trust is not achieving the 18 weeks target with a “low assurance” that the situation will change quickly.

NHS South Central has identified four trusts with problems “focused principally on the build-up of backlogs”.

In the South West 1,445 patients waited longer than 18 weeks for inpatient treatment in November - 417 at the Royal Cornwall Hospitals Trust.

However, NHS North East expects all its trusts to meet the 18 week target at the end of the financial year.

National figures from the Department of Health for November last year show trauma and orthopaedics and neurosurgery were already below 90 per cent achievement for admitted patients.

The Department of Health has confirmed that “exceptional circumstances” such as the weather can be taken into account by the Care Quality Commission when assessing performance and by primary care trusts when assessing financial penalties, but the raw data will be posted on its website. The January data is likely to be released in March.

The effect of the snow was varied, with some trusts dealing with massive increases in emergency cases, leading to cancelled elective operations, and staff struggling to get to work. In addition, norovirus cases affected many hospitals.

Waiting times in accident and emergency were also affected - with a 12 hour trolley wait being reported at Hinchingbrooke Hospital in Cambridgeshire and all SHA areas missing the four hour target for the week to 27 December.

Ambulance response times also slumped.