CROYDON University Hospital's new IT system has led to increased waiting times and information about some patients to be lost.
The Cerner computer system, adopted last September, was supposed to cut down on paperwork and provide clinicians with more detailed information about patients.
But this week Croydon Clinical Commissioning Group (CCG) board members expressed serious concerns about ongoing problems with the system.
Fouzia Harrington, director of quality and governance said: "The implementation [of Cerner] itself went well in technical terms, but there have been some implications about how it has been used by staff.
"It's had far more impact in terms of the time it takes to book people in, for example. There have also been implications in terms of lost information about patients.
"There has been a lack of information about hospital activity, which has an impact on finances and, potentially,the quality of services patients are receiving.
"We're working with CHS to understand [the issues] but we have received assurances in terms of there being no harm."
David Hughes, a lay member of the board, was not satisfied with that reassurance.
"You say that no harm has occurred," he said, "but while we've had no direct incident so far, patient care has definitely suffered.
"You talk about increased waiting times and there's a risk that harm may occur because of the difficulty in getting in touch with clinicians who actually know what is going on with the patient.
"I'm very concerned from a quality point of view that our main provider has a serious problem with its information systems.
"We should be taking action. There may not have been an incident we are aware of, but it may actually come out through further investigation that there has been. This is actually very serious."
As well as increasing waiting times across various areas of the hospital, missing information since September means the CCG cannot be certain of exact levels of activity at the hospital, making decisions on what services to commission more difficult.
The concerns were raised at a board meeting on Tuesday.
Dr Tony Brzezicki, chairman of the CCG, acknowledged the issues but expressed confidence that the new system would eventually lead to improvements.
He said: "Hospital patients had five sets of notes before. That in itself posed a risk that Cerner will mitigate.
"However, there have been administrative delays which mean longer waiting times for patients.
"There are also issues for the service to primary care which is a significant risk.
"Some of the problems have been resolved though I am concerned at the time scale because they are certainly impacting on my practice."
The Advertiser asked Croydon Health Services, which runs the hospital, a series of questions about Cerner, including its cost to the NHS, but was sent a short statement.
A spokesman said it would improve patient administration and mean nurses have access to "quality, detailed information" when delivering care.
He added: "During the initial switch over of systems in September while staff were getting used to the system, some patients did need to wait slightly longer to check in for their clinic appointments.
"The trust has maintained and surpassed our 18 week referral to treatment targets from the initial roll out."
