The Information Commissioner's Office is investigating problems with a national service for transporting patient records after GPs complained some were going missing.
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.
It has contracted CitySprint, a courier service, to move the records around.
Pulse magazine revealed that some GP practices have reported being sent the wrong patient records or those of patients who have died.
There was one report that patient records were found in a car park, while other GPs have said supplies have gone missing and payments have been delayed.
Peter Harrison, a practice manager in Weston-super-Mare, said his practice received 26 correct records in one week, but also some for patients who "never had any links with the local area at all" and some "registered with practices far away".
He said he also received records for two dead patients.
A spokesman for the Information Commissioner's Office told Pulse: "The ICO has been made aware of concerns around the process for moving GP patient records within England, and is making inquiries."
NHS England said: "We will continue to work closely to monitor, review progress and investigate any issues raised by users... reported issues are routinely logged and investigated to determine root causes and the appropriate remedial action in line with NHS England information governance procedures."
A spokesman for Capita said: "We take information governance very seriously. Any issues reported to us or NHS England would be investigated in accordance with NHS England's information governance process."
The British Medical Association's spokesman on the issue, Ian Hume, told Pulse it had raised "governance issues" with NHS England.
He said: "When they started they didn't have containers to put it (notes) in, now they've issued CitySprint with containers so you have boxes which can be sealed. So the CitySprint driver comes in with a sealed box, you fill it up and that's sealed up so it won't fall over. Rather than the story we had of somebody walking out with a bundle of notes in their hand, who has dropped some in the car park.
"My advice is, if a practice receives the wrong set of notes, then this needs to be returned to Primary Care Support England via Capita, and it needs to be reported officially as an information governance breach."
Dr Hume said GP practices were also complaining about courier drivers not carrying ID or properly signing for records.
A CitySprint spokesman said: "We are working closely with Capita to introduce a new, secure weekly collection service for medical records for all GP practices across England.
"All CitySprint couriers carry mandatory ID and nothing should be handed over unless ID is presented. We take information governance seriously and would urge anyone with concerns to report them through the proper process."