The North East Ambulance Service has admitted past failings - in the quality and speed of information given to coroners investigating the deaths of patients.
It has also apologised to the families of those involved.
The admission follows a Sunday Times investigation which said staff at the service first raised concerns in 2019.
NEAS confirmed this and said two independent investigations were issued with reports released in 2019 and 2020, which found improvements were needed.
They also say a police investigation found no evidence of more serious allegations that the Trust had deliberately failed to disclose, hide or destroy evidence.
The service says it has made significant improvements and its procedures relating to coroners are now independently audited.
Helen Ray, chief executive of North East Ambulance Service, said: “We accept that there were historical failings and we have listened and acted upon the concerns raised by staff of the quality and timeliness of documents disclosed to coroners.
“Utmost in our mind are the families and we unreservedly apologise for the distress we have caused to them.
“The claims made that we continue to fail in respect of disclosure are incorrect. A member of staff does continue to have concerns, but we have continued to act when concerns are raised. We have reaudited our process, have discussed with coroners and with the CQC and have embedded regular reviews to ensure these issues cannot reoccur. We are confident that the system in place is robust.
“The Care Quality Commission formally responded in late 2020 to confirm they had closed the matter with no further action deemed necessary.
"Northumbria Police, who were involved when a member of staff was dissatisfied with our actions, have also confirmed this matter is closed with no action taken on the basis there was no evidence to support the allegations put to them.
“Many of the cases passed to coroners relate to the timely response of an ambulance to an emergency call. It has been widely reported that the delays in reaching patients have become an issue across the country, not just in the North East. We are working closely with our commissioners, following a significant investment in our service over the next 12 months, to improve our response performance.”