Nearly 40,000 patients in Nene are waiting at least three weeks to see a GP, new figures reveal.
Doctors say it is important to treat patients early to “avoid conditions getting worse”.
NHS Digital data shows that 37,140 people in the Nene Clinical Commissioning Group had to wait until at least 21 days to see a doctor after booking an appointment in October 2018.
That is 11% of all patients.
Of them, 18,800 waited more than a month.
Waiting times were in line with November 2017, the earliest period for which data is available..
The Patients Association said the impact of the waits “should not be understimated”.
Rachel Power, the charity’s chief executive, said: “It can be incredibly stressful to face a long wait before getting to see a doctor, quite apart from prolonging the length of time someone has to live with the medical issue that is troubling them.
“All of this is a symptom of an NHS running at boiling point all year round.”
Professor Helen Stokes-Lampard, chairwoman of the Royal College of GPs, said it was “frustrating” that patients were having to wait too long to secure a GP appointment.
“We want to deliver timely care to patients, in the early stages of illness, to avoid conditions getting worse, when they can be both more distressing for patients, and more costly for the NHS,” she said.
Nearly half of patients in Nene CCG were able to see a GP the same day the appointment was made.
Experts say the figures include patients who need regular appointments and are likely to be booking ahead.
Nationally, 10% of patients waited on average at least three weeks to see a GP in October 18, compared to 9% in November 2017.
A Department of Health and Social Care spokeswoman said: “GPs are working hard to provide high-quality care to their patients, with over a million appointments booked every weekday in October and 40% of patients being seen on the same day.
“We are also rolling out extended access hours across the country to ensure that patients can find appointments in the evenings and at weekends, making it easier for people to see a doctor, nurse or other health professional at a time convenient to them.”
Across England, doctors see around one million patients every day, with Mondays shown to be the busiest day of the week.