The HSE has confirmed around 400 women have received letters from CervicalCheck containing incorrect information.
800 women, whose repeat smear test results were delayed for months, got a letter this week telling them their HPV status was unchanged and 'remained negative'.
However, around half of the women should have been told their HPV status 'remained positive'.
The HSE has apologised for "any confusion or distress" the mistake may have caused.
The executive said: "These women’s recommendations remain unchanged and they would have received appropriate follow up care at the time.
"We are nonetheless again very sorry for any confusion or distress this error may have caused.
"We will be writing to women involved, as a matter of priority, to clear up any confusion they may have."
Anyone with questions or concerns about the issue can contact firstname.lastname@example.org or by phone at 01 865 9392.
Labour TD Alan Kelly said administrative errors such as this are "inexcusable".
He argued: “The question needs to be asked after everything that has happened in the last 18 months why are there no proper checks and balances before women are contacted by CervicalCheck?
“Messy errors like this are completely avoidable. This kind of carry on is not good enough from CervicalCheck when it is under so much scrutiny still."
Sinn Féin's Louise O'Reilly, meanwhile, said the situation is "almost surreal".
She called for a root and branch reform of the national screening programme.
The latest development comes in the same week as the publication of a rapid review of an issue involving CervicalCheck.
Prof Brian MacCraith's report revealed more than than 4,080 women had delayed results communicated to them as a result of an IT problem at a US lab.