British Prime Minister Theresa May has angered GPs as she claimed they needed to do more to reduce the burden on the National Health Service (NHS).

May's statement follows weeks of mounting chaos in the service, particularly in accident and emergency units, where four-hour patient waiting times are routinely missed.

At one hospital, one woman reportedly died of a heart attack after suffering a 35-hour wait on a trolley, while a man suffered an aneurysm waiting on a trolley. A third patient was also found hanged in a suspected suicide.

Experts and campaigners have repeatedly said the NHS is critically underfunded and the British Red Cross labelled the situation a "humanitarian crisis", however May and Health Secretary Jeremy Hunt has refused to heed their calls.

Instead, she said the NHS had received more money than it asked for – a claim which NHS chief executive Simon Stevens said was "stretching the truth".

Now, in a move that will trigger more frustration, May said GPs need to make more effort to provide a seven-day NHS, to reduce the pressure on A&E units.

In a statement, she said: "Most GPs do a fantastic job and have their patients' interests firmly at heart.

"However, it is increasingly clear that a large number of surgeries are not providing access that patients need – and that patients are suffering as a result, because they are then forced to go to A&E to seek care," said May. "It's also bad for hospitals, who then face additional pressure on their services."

She said GPs will risk having their funding cut if they do not provide a 12-hour service, seven days a week.

Following the statement, the prime minister was accused of "scapegoating" GPs for the crisis that was created by the Conservative government.

Dr Chaand Nagpaul, chair of the British Medical Association's GPs committee, said: "This is not the time to deflect blame or scapegoat overstretched GP services, when the fundamental cause of this crisis is that funding is not keeping up with demand.

"This is evidenced by the fact the UK spends less on health and has fewer doctors and beds per head than other leading countries, as highlighted by the head of NHS England, Simon Stevens, only this week.

"Rather than trying to shamelessly shift the blame on to GPs, the government should take responsibility for a crisis of its own making and outline an emergency plan to get to grips with the underlying cause, which is the chronic under-resourcing of the NHS and social care."

Nagpaul said GPs already provided care around the clock through their involvement in GP out-of-hours schemes and that many practices already offered evening and weekend appointments.

"However, there are examples where extended opening has been abandoned due to lack of demand," he added. "Government funding for extended opening has also been halved in some areas."

Professor Helen Stokes-Lampard, chair of the Royal College of GPs, said: "It's extremely unfortunate that the prime minister is being reported as pushing forward with a misguided scheme to force GP surgeries to offer routine services from eight-to-eight, seven days a week, regardless of patient demand or local resources."

She added: "It has never made sense to force GPs to offer services that there is little patient demand for. In many cases, practices have already had to actually stop offering extended opening hours because of a lack of patient demand for them.

"Blaming GPs for the crisis facing our NHS is not going to help anyone. Instead, we need to start investing in our health service properly, so that there are adequate resources and clinical staff to deliver the care our patients need and deserve."