Inspectors raised "serious concerns" about patient safety at one of England's main abortion providers.
Marie Stopes International temporarily suspended some abortions services in August when the concerns were raised by the Care Quality Commission (CQC).
In one case, doctors did not ensure a woman with learning difficulties fully understood the procedure, the watchdog found.
MSI said it had made "considerable changes" since the inspections.
The CQC allowed all services to be resumed by the end of October.
Inspectors visited 12 of the group's sites in England between April and August.
The report found that 2,634 incidents had been recorded at MSI locations between 2015 and 2016 - a rise of 704 from the previous year - but the organisation had provided "limited" explanation as to why this had happened.
The charity performs 70,000 abortions a year, about a third of all procedures performed across England.
Some staff obtaining consent from patients appeared to have insufficient knowledge of procedures, the CQC said.
Prof Edward Baker, deputy chief inspector of hospitals at the CQC, said: "Our concerns at a corporate level - particularly around governance arrangements, staff training, and around patient safety and safeguarding protocols - did not give us the necessary assurance that patients would be protected from avoidable harm at all times, that possible safeguarding concerns could be identified and that incidents could be reported and learned from.
MSI voluntarily suspended the termination of pregnancies for under-18s and vulnerable women for seven weeks earlier this year following the unannounced inspections.
It also halted terminations under general anaesthetic or conscious sedation and suspended all surgical terminations at the provider's Norwich centre.
The CQC said the organisation had made progress since the inspections and allowed it to resume services in October.
By Robert Pigott, health correspondent, BBC News
Although the CQC's report draws attention to the case of a woman with learning difficulties who was not adequately counselled by Marie Stopes, its report reflects not so much a number of egregious mishaps as a general sloppiness in procedure and training.
The watchdog's report contains a litany of shortcomings that reflect a general lack of care.
They included an ad hoc approach to checking the competency of anaesthetists, doctors and other staff, and a failure to make sure equipment was well maintained.
Poor standards in Marie Stopes' training worried inspectors, not least in the context of the vulnerability of many of the women using the charity.
They found that staff taking consent from children and young people were not appropriately trained to explore issues such as female genital mutilation or sexual exploitation.
Given the sheer scale of Marie Stopes' service, it's not hard to understand the inspectors' concerns.
Professor Baker said the CQC would continue to monitor the group, adding: "We will not hesitate to take further action, if necessary in order to guarantee this provider meets the standard of care we expect and that its patients deserve."
Suzanne Ash, interim managing director at Marie Stopes UK, said MSI had learned from the inspections.
She said: "We have worked hard with the Care Quality Commission to regain compliance and we're grateful to them for their assistance.
"Since the inspections, we've made considerable changes to our management, governance and assurance processes, including extensive training of staff, and updating of policies".