Statistics from NHS England show a total of 18,155 patients were waiting for non-urgent elective operations or treatment at the end of July - the latest figures available.
It’s a slight decrease from June’s figures of 18,168, but much higher than the 11,000 waiting in July last year.
Of those, almost 60 had been waiting for more than a year to be seen.
The average wait time from referral to treatment at the hospital was nine weeks - up from eight weeks the month prior.
Richard Murray, chief executive of the King’s Fund think-tank, said the NHS is being ‘shaken to its core’.
“The challenges affecting the NHS cannot be solved without addressing the systemic workforce shortages and sustained funding shortfalls in social care,” he added.
“The new PM and Secretary of State have a matter of weeks to decide what emergency short term action to take to provide at least some additional support during what promises to be a terrible winter for patients and staff.
“This could include maximising the campaigns for winter Covid boosters and flu vaccines, tackling the pensions issue driving senior staff out of the NHS, and emergency funding to boost capacity in social care.”
More than 2,800 patients were also waiting for a key diagnostic test - such as an MRI scan or gatroscopy - in July.
Almost 15 per cent of those had been waiting for at least six weeks.
Nigel Edwards, chief executive of the Nuffield Trust, said the NHS’ problems have been ‘years in the making’.
“The new government is absolutely right to prioritise health and social care as a matter of urgency,” he added.
“Exactly how to turn this around as we go into winter will not be an easy task, but a relentless focus on the workforce, social care and hospital buildings are essential.”
Further figures from NHS England show that of the 42 patients which were ‘urgently referred’ by their GP and treated at Barnsley Hospital, 27 were receiving cancer treatment within two months.
In June when 56 patients were urgently referred, 41 were treated in the same time frame.
New Health and Social Care Secretary and Deputy Prime Minister Therese Coffey said: “Clearly this level of performance is unacceptable, which is why I have set out our priorities will be ABCD - ambulances, backlogs, care and doctors and dentists.
“We know some of the backlog challenges will increase as people continue to present themselves for treatment.
“We are investing £39 billion to tackle these challenges, ensure the NHS is fully prepared for winter and fix the broken social care system.”