Urgent enforcement action has been taken against a GP surgery after inspectors found mismanagement of hospital letters put patients at risk.
Moredon Medical Centre, in Swindon, was visited by the Care Quality Commission (CQC) on 11 April.
It found thousands of hospital letters and patient prescriptions had not been reviewed within appropriate timescales.
Moredon said that since the inspection it had "reviewed and responded to 98% of the outstanding correspondence".
The CQC's deputy chief inspector said it was "extremely concerning" the centre had not notified the watchdog of the backlog before inspectors visited.
The surgery is one of five in the town with its back-office management and IT services run by Integral Medical Holdings (IMH).
The company recently agreed to end all its contracts in the town after complaints over long waits for appointments and blood test results.
In a report, the CQC said staff had also not received appropriate support or training, and had reported excessive work-loads.
It added certain systems and processes to manage patient correspondence "were not effective or efficient and could have placed patients at risk of harm".
Inspectors identified "approximately 10,000 hospital letters (and correspondence from other sources), some of which were dated from 2018, had not all been reviewed within two days of receipt".
Deputy chief inspector Ruth Rankine said: "Despite staff trying their best the practice was failing its patients and team."
The provider must now demonstrate what action it is going to take to meet regulations.
The CQC had previously inspected the surgery on 7 March, to follow up on a warning notice issued after inspections in November.
It said at the March inspection it had made changes and all the failings had been addressed.
Swindon's Clinical Commissioning Group (CCG) did not wish to comment on the report.