Thousands of Sutton residents are believed to have experienced problems registering with a GP, prompting concern for the future of healthcare in the borough.

A questionnaire asking people if they had problems getting on to a GP list was sent to 40,000 households in the Carshalton and Wallington constituency by MP Tom Brake last month.

He said in six per cent of the responses he has received so far, residents said they had experienced difficulties. But he believes this could be the tip of the iceberg in his constituency and estimates out of 80,000 people, about 5,000 would have experienced problems.

In the neighbouring constituency of Sutton and Cheam, elderly residents have written to MP Paul Burstow reporting difficulties when trying to move to a nearer more convenient surgery, with problems particularly bad for those living in sheltered housing.

Mr Burstow said: "It is appalling that those affected by closed GP lists are some of the most vulnerable in society. Health problems may be ignored and trips to the doctor postponed because of the difficulties in getting to the surgery."

The problems for Sutton residents could have wider repercussions for healthcare in the borough, as proposals are underway to make GPs responsible for more kinds of treatment. The Better Healthcare Closer to Home initiative intends to give people NHS treatment closer to where they live, using places such as GP surgeries, patient's homes, local clinics or local care hospitals.

Mr Brake told the Guardian: "The problems with getting on a GP list has long-term implications for healthcare in Sutton. The current Better Healthcare Closer to Home initiative will result in more work being done by GPs and as people are already having difficulties registering with a GP it poses a question over the whole scheme."

Sutton and Merton Primary Care Trust (PCT) said patients who have problems getting onto a GP list should contact them.

A spokesman said: "We have recently offered another 13 practices in Sutton additional funding, which will lead to an increase in the practices' clinical workforce.

"This will enable greater access for patients to a GP or a primary care professional."

Anyone with problems registering with a GP can call 020 8335 1400 or access the PCT Patient Advice and Liaison Service on 0800 085 3182.