Nearly half of ambulance patients arriving at the Somerset Trust were delayed by at least 30 minutes last week, new figures show, as response times across the country rocketed.

Health think tank the Health Foundation said the roots of the NHS crisis "lie in political choices made over the last decade".

The figures come as around 25,000 ambulance workers from the Unison and GMB unions – including paramedics, call handlers, drivers and technicians – went on strike this week.

Workers are striking over demands for an inflationary pay rise, but the Government says most staff have received a 4% pay rise.

NHS England figures show 124 patients waited at least one hour in the week to January 8, while a further 102 patients waited more than 30 minutes across the same time period.

It meant 48% of the 466 ambulance arrivals at Somerset NHS Foundation Trust were delayed by at least 30 minutes – though this was down from 58% the week before.

At least 431 hours were lost as a result.

Further NHS England figures show the mean response time by ambulances in England to category two calls, which include suspected heart attacks and strokes, was one hour, 32 minutes and 54 seconds in December – the longest on record and more than five times the target of 18 minutes.

Similarly, response times for urgent calls, such as late stages of labour, non-severe burns, and diabetes, averaged four hours, 19 minutes and 10 seconds – again, the longest on record.

Meanwhile, response times to the most urgent incidents, defined as calls from people with life-threatening illnesses or injuries, rose to a record 10 minutes and 57 seconds and well above the target of seven minutes.

Sarah Scobie, deputy director of Research at health think tank, the Nuffield Trust, said: "Too many patients needing an ambulance in the lead-up to Christmas faced horrific waits.

"Despite the best efforts of ambulance staff, they still face lengthy delays to handover patients safely to hospital teams, who are themselves working at capacity."

Tim Gardner, senior policy fellow at the Health Foundation, said: "There are no quick fixes – if the Prime Minister wants to live up to his promise to cut waiting lists without tricks or ambiguity, the first step is to be honest with the public about the scale of the crisis and what it will take to get the NHS back on track.

"The pressures on the NHS result from a decade of underinvestment in the NHS and other public services, a failure to address chronic staff shortages, raiding capital budgets and the longstanding neglect of adult social care."

Nationally, nearly one in five (19%) ambulance patients waited more than an hour to be handed to A&E teams last week – down from a record 26% the previous week.

And 36% of ambulance patients waited at least 30 minutes to be transferred to A&E, down week-on-week from a record 44%. The equivalent figures for this point last year show 10% of patients waited over an hour and 23% waited at least half an hour.

NHS national medical director, Professor Sir Stephen Powis, said: "As staff responded to record A&E attendances, 999 calls and emergency ambulance callouts as the 'twindemic' led to unprecedented levels of respiratory illness in hospital, they also continued to deliver for patients."