The British Red Cross is now working in 20 A&E departments in the UK amid what the charity describes as a 'humanitarian crisis' in the National Health Service.

Mike Adamson, the charity's chief executive, told The Times the BRC has seen a "significant change" in demand for its help, driven by inadequate funding for social care and a "plethora" of other failures across the system.

In a statement, the charity said it is "on the front line, responding to the humanitarian crisis in our hospital and ambulance services across the country," having been "called in to support the NHS and help get people home from hospital and free up much-needed beds."

Painting a grim picture of the status quo, Adamson describes how the charity has "seen people sent home without clothes, some suffer falls and are not found for days, while others are not washed because there is no carer there to help them".

"If people don't receive the care they need and deserve, they will simply end up returning to A&E, and the cycle begins again."

Prime Minister Theresa May has, however, rejected the notion of a humanitarian crisis in the NHS. She told Sky News: "I don't accept the description the Red Cross has made of this".

"There are pressures in the NHS, we see those pressures. We have an ageing population, this brings pressures, particularly in the interface between the health service and social care.

"We have taken some immediate steps in relation to that issue but we are also looking to ensure best practice in the NHS and looking for a long-term solution to what has been a problem that has been ducked by government over the years."

The Royal College of Emergency Medicine is also warning that emergency services are in "a state of crisis", facing the worst four hour performance in almost 15 years.

In the week leading up to Christmas, there were 332,118 attendances in England alone, but an average of 87.6 percent of all beds were occupied - above the recommended safety limit, it said, noting that the number of patients experiencing delayed transfers of care has leapt 28 percent in a year.

The College's Winter Flow data - which looks at the flow over patients over the winter period - suggests that average four hour performance, a key barometer of pressure on the NHS, was around 77 percent with some Trusts struggling in the 50-60 percent range, well below target.

"Our expert view is that this type of performance leads to serious safety issues. Data so far also suggests a year on year drop in performance in the range of 4 to 11 percent," it warned, and added that "overcrowded departments, overflowing with patients, can result in avoidable deaths".

"The emergency care system is on its knees, despite the huge efforts of staff who are struggling to cope with the intense demands being put upon them," said Dr Taj Hassan, President of the College.

"Internal major incidents are being declared in many systems around the country – every hospital in Essex has been on 'black alert' – and staff in Emergency Departments (EDs) are working at and beyond their capabilities. This cannot be allowed to continue."

"While at a local level there may be a case to be made around the need for better service planning, the ultimate problem is a national one - our emergency care system is clearly underfunded.

"A correction to the funding of both the NHS and social care has never been more vital, and further cuts in the form of Sustainability and Transformation plans in England, if carried through, would be potentially catastrophic," he warned.

The BRC is also calling on the government "to allocate immediate funding to stabilise the current system and set out plans towards creating a sustainable funding settlement for the future".

However, May told Sky News that "funding is now at record levels for the NHS".