Leading doctors have raised concerns over a private firm which provides support services to GPs.
Earlier this year, NHS England has commissioned private firm Capita to run the Primary Care Support England service, which handles GP payments, medical supplies, moving records and patient registrations.
But the British Medical Association (BMA) said that "systematic failures" by the company could be inhibiting GPs' abilities to provide safe care.
It said that GPs had told the union there are serious problems with the management of patient records including long delays with the collection and delivery of records, wrong records being delivered to practices, and problems processing urgent requests for records in a timely manner.
The BMA said that doctors had also reported problems with the supply of essential equipment such as prescription pads, fit note certificates and syringes to GP practices.
Dr Chaand Nagpaul, chair of the BMA's GP committee, said: "Clear evidence is emerging that there are a range of systematic and endemic failures in the way Capita are running crucial back office support services in general practice.
"Local GPs are reporting to the BMA that they are facing unacceptable delays in patient record transfers and mistakes in maintaining supplies of crucial medical equipment, like syringes and even prescription paper.
"These mistakes are directly impacting on the ability of many GPs to provide safe, effective care to their patients. They are in some cases being left without the essential information they need to know about a new patient and the tools to treat them.
"NHS England is ultimately responsible for the chaos caused by trying to cut the cost of this essential service for practices by privatising it and we can now all too clearly see the result, with practices picking up the workload and patients suffering as a result.
"I have written to NHS England expressing my grave concern about this state of affairs and received an apology for these failures. But we need urgent action to correct these shortcomings before patient care is further compromised."