As junior doctors begin a four-day strike today with a two-day strike by consultants a fortnight later, Sir Julian Hartley, chief executive of NHS Providers, said:

"Trust leaders are very worried about six more days of severe disruption across the NHS this month.

"We could be close to a tipping point. Trusts and staff are pulling out all the stops to reduce waiting times for patients but with no end to strikes in sight the sheer volume of planned treatment being put back due to industrial action will make it almost impossible for trusts to cut waiting lists as much as the government wants.

"Waiting lists are now at a record high of 7.57 million, the pressure on urgent and emergency care services is relentless and an already stretched NHS is gearing up for another high-demand winter as pressure on tight budgets mounts.

"A string of strikes – which have led to more than 835,000 routine treatments and appointments being put back since December – is estimated to have cost the NHS around £1bn already including lost income and hiring expensive staff cover.

"The number of rescheduled appointments could be close to 1 million after this month's strikes and consultants have called another two-day strike in September. There will be a long-lasting effect on patients who have had treatment delayed and on already low staff morale.

"Concerns are mounting too over how patient safety will be maintained during August's strikes as many NHS services will be even more stretched as many staff are on much-needed summer holidays and cover is harder to secure.

"It's vital that the government and unions find a breakthrough urgently. Trust leaders understand the strength of feeling among striking staff and why they're taking action. Everyone in the NHS wants to concentrate on treating more patients more quickly rather than spend days making plans to cope with strikes.

"People can still rely on the NHS during strikes, calling 999 in an emergency. For less urgent cases people should use 111 online for help and advice."