Health service experts are warning that the NHS could be “sorely tested” in the coming months as it is already running at near maximum capacity with “severe pressure” on the horizon.

NHS Providers says while the NHS has done all it can to prepare for a difficult winter season, there are continuing difficulties and pressures “that could jeopardise trusts’ ability to cope”.

According to its briefing paper Ready and resilient? How NHS trusts have prepared for winter, the health service is already running at 87 percent bed occupancy - above the 85 percent target - and patients are still facing discharge delays, which is bottlenecking the system.

Added to which, shortages of key staff groups including paramedics, GPs and A&E consultants and nurses, are magnifying the strain, as are funding issues, with the additional NHS funding for winter in the Budget coming “very late to be used to maximum effect”.

All this is leaving some hospitals running with capacity as high as 99 percent, health bosses are warning.

“We’re lucky to get below 99 percent bed occupancy rates,” the chief executive of one trust told the Guardian. “We plan for winter all year round, but there’s an underlying lack of beds and resources.”

This could pose a huge problem given that this year’s flu strain is potentially the worst seen in two decades, “having already placed health systems in Australia and New Zealand under severe pressure earlier this year,” NHS Providers notes.

“Winter always presents a big challenge to the NHS. Last year the pressures were intolerable. Services were stretched up to, and in some places beyond, breaking point,” said its chief executive, Chris Hopson.

“This time preparations have never been more thorough,” he noted, but also “we are not where we would want to be as we head into winter. We can not say with certainty how tough this winter will be, but the likelihood is that services will be sorely tested.”

Commenting on the report, Nick Scriven, president of the Society for Acute Medicine, warned that there is “a real sense of foreboding that this may be the winter that finally breaks the backbone of the service.”

“While staff on the frontline will, as always, pull out all the stops to provide safe care, the fact remains the NHS is 1,400 beds short of what it needs this winter.

“The fear is that we have not faced an infection crisis over winter for several years and if the Australasian experience is repeated here the system will be swamped as never before.”