An additional 3,591 women have not received information about NHS cervical cancer screening, it has emerged.
Capita, the company contracted to send out the screening invitations, made the discovery while investigating an administrative error already known to have affected 40,000 women in England.
NHS England says there is no evidence of any harm having resulted from these issues, now dating back to 2017.
The women involved, and their GPs, are being written to.
The errors were made in 2017 and 2018.
Most of the unsent letters were invitations or reminders to attend for screening but some were about abnormal test results.
Capita says that these 200 or more women with abnormal results still had the correct clinical follow-up investigations despite the correspondence failure.
The intended recipients should have received at least one notification from their GP or screening clinic – as women with abnormal results should be sent letters from two or three sources, not just Capita on behalf of Primary Care Support England.
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About 4.5 million women aged 25 to 64 receive invitations for screening each year.
Those aged 25 to 49 are offered screening every three years, with the older age groups invited every five years.
All those who did not receive an invitation letter or reminder have been written to.
A spokesman for Capita said the company "apologises" for the mistake.
He said the correct process for "uploading, organising and checking" had not been followed and appropriate disciplinary action was being taken.
The senior manager responsible for the contract has left the company.
An NHS England official said: "There is no current evidence of any harm having resulted from these issues and all women affected, and their GPs, are being written to today advising them on what they need to do.
"These administrative failures were uncovered by a clinically led panel, convened by NHS England following a serious incident confirmed by Capita earlier this year.
"Primary Care Services England, run by Capita, has accepted its responsibility for these errors."
Robert Music, chief executive of Jo's Cervical Cancer Trust, said: "Frankly, it is appalling that thousands of women have been affected by a further error. At a time when cervical screening attendance is falling, we cannot afford for faith to be lost in the programme. This could result in more women not taking up their invite. Waiting for results can already be an anxious time and failures such as this are only adding further stress to women."
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