The waiting list for planned care has exceeded the 3 million mark, while emergency admissions are continuing to rise, the latest activity data shows.

The elective waiting list stood at 3.1m in May, the information published yesterday showed.

Waiting times expert Rob Findlay said the size of the list was likely to mean it would be increasingly difficult for trusts to meet the 18 week referral to treatment time target for admitted patients.

He said: “Fundamentally the waiting list is growing. As far as I can work out, 3 million is the danger level for the admitted patient target, it’s not hard and fast but I’d say the waiting list is in the danger zone.”

The Department of Health last month announced £250m additional funding to help trusts deal with backlogs of patients waiting for elective treatment.

However, Mr Findlay said the elective fund was only a short term fix for a long term problem. He said: “What they’ve done is to throw a waiting list initiative at it in the hope that this will kick the can down the road to the other side of the election leaving the structural baseline deficit on activity as a problem for the next government to solve.”

Richard Murray, director of policy at the King’s Fund, said: “It’ll end up like A&E where you’ll have to put money in every year, and not only every year, but it’ll have to go up because all you’re doing is a very short-term fix, a plaster, over what threatens to be a long-term problem – that we can’t meet the demand that’s there under the current way we deliver services.”

Mr Murray said that despite a “recruitment binge” for extra nurses and doctors this had not lessened pressure on the system. He said: “It might be that we’re coming to the fact that everywhere the system is creaking because this is year four of year five of not having any money and even with the extra staff in there it just isn’t enough.”

Dame Barbara Hakin, chief operating officer for NHS England, said: “Whilst all the required standards are achieved this month we are not complacent and we will be working hard with frontline staff over the summer months to treat even more patients.”

Meanwhile, the number of emergency admissions at major accident and emergency departments in the first quarter of 2014-15 was the highest for any quarter since records began – at 992,559. It continues a trend of increases.

Clifford Mann, an emergency medicine consultant and president of the College of Emergency Medicine, said the “biggest problem” in emergency departments was the build up of patients waiting to be admitted to wards.

He said: “Exit block is the most pernicious way to grind a department to a halt because if you can’t move people from the department to the wards, you can’t offload the next patients from the ambulance.

“That’s obviously bad but then you’re also trying to run a ward and an emergency department with the same number of nursing staff and that overstretches them.”