A six-year-old boy died from a treatable blocked bowel disorder after his father made repeated calls to NHS call handlers and his doctor’s surgery asking for help, an inquest heard.

Sebastian Hibberd suffered vomiting, diarrhoea and was in excruciating pain during the weekend before his death on Monday 12 October 2015.

His father, Russell Hibberd, told the inquest in Plymouth that three separate call handlers from the NHS 111 service failed to recognise the seriousness of his son’s condition. He said that despite several calls to his GP surgery he was not able to speak to a doctor, though he was promised a callback by reception staff.

Hibberd told the inquest that Sebastian, who was otherwise healthy and fit, fell unwell on the morning of Saturday 10 October 2015. He tried to get help for his son but Sebastian died two days later, shortly after arriving in hospital. A postmortem revealed he died from a blocked bowel disorder.

Hibberd said: “There was a huge probability that he would have recovered if he was seen urgently. His death was avoidable and very difficult for me and my family to process. Three of the four 111 call handlers failed to realise the severity or recognise the red flags. Why was I not transferred to a clinical practitioner at any time during the calls?

“Five occasions I tried to make contact with the surgery during opening hours and was only ever able to speak to a receptionist. There has been no satisfactory explanation.

“I never received a call back from the doctors. I was promised one, but one was never received. I have serious concerns about the organisational failures responsible for Seb’s death and seek assurances this will not happen again.”

Hibberd said he first noticed something was wrong when his son could not keep food or water down. He said: “He was vomiting more than once an hour and he spent most of the day watching films in bed with a bucket beside him.”

Dr Georgina Selby, a consultant paediatrician at Derriford hospital in Plymouth, said some of the symptoms described by the father to the 111 service should have raised red flags, including dark green vomiting and that the boy appeared confused and had cold hands and feet. “They are markers for serious illness in children,” she said.

The inquest continues.