Taoiseach Leo Varadkar has said the Government will consider an independent inquiry into failings in audiology services provided to children in Ireland.
Almost 60 families in the west of the country have received apologies in recent weeks for failings in audiology services provided to their children.
It is the second time in less than a year that the HSE has had to apologise for audiology failings.
Last year, RTÉ Investigates revealed serious failings in paediatric audiology services provided to another 49 children in counties Mayo and Roscommon, some of whom were left with lifelong impairments.
The findings were contained in a look-back review of care provided by one audiologist from 2011 to 2015.
The audiologist in question no longer works in the Republic of Ireland.
Mr Varadkar was responding to a question in the Dáil by Sinn Féin leader Mary Lou McDonald about the issue.
The Taoiseach said the priority now is to disclose and to make sure that those who need medical care and educational supports get them.
He said the clinician who carried out the hearing test is responsible for the mistake, and that the people who made the mistakes are no longer working for the health service.
Mr Varadkar said the Health Service Executive Assistant Clinical Lead for audiology identified the problem and acted on it.
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RTÉ Investigates has now learned that in recent months the HSE has written to an additional 57 families to inform them they have also been affected.
As before, all these children had attended the same audiologist.
"We are so disappointed by this development," said Martin Corcoran.
He is a member of the support group set up for affected families and whose daughter was among almost 50 children to feature as part of the original review.
"We were repeatedly reassured last year by both Government and the HSE they were satisfied they had reviewed all cases and they were happy everyone who needed to be contacted had been contacted and now here we are learning about new cases."
It is understood that the additional 57 cases will now form part of a second look-back review, however families have not been given any indication as to how long that process will take.
Among those affected is 11-year-old James from Co Mayo. His parents say they were entirely unaware of James's hearing loss until they recently received a letter from the HSE apologising for the care he received.
James's mother Denise said his delayed diagnosis has resulted in serious consequences for him.
She said: "Six years ago we were told James's hearing was fine and then we received this letter and to be honest at first we didn't understand what it meant.
"Then to be told about James's hearing loss - we were shocked. Six years ago James was in Junior Infants, now he is in Fifth Class and in that time he has had absolutely no intervention for his hearing loss.
"There is no doubt it has had a huge impact on his school work and in his interaction with his school peers. James also has other issues and we used to put his distraction down to his dyspraxia diagnosis, but now in hindsight we see many of his difficulties were because he couldn't hear."
For Denise and the other affected families, they say getting immediate access to services is now vital because "time is running out" for their children who in some cases have already missed out on eight years of hearing support at a key developmental phase in their lives.
In a statement to RTÉ, the HSE said the original look-back review related to children aged under four, and it was as part of that process some children aged over four years were also found to have been "discharged from the service without a follow up appointment".
The HSE added: "The Over 4's group were not followed up at an earlier stage as the Preliminary Risk Assessment did not flag them as an area of concern."
But it says to date "no moderate or major incidents" have been identified.
However, these latest developments have caused some parents to lose faith in the HSE process and they are now calling for a thorough independent investigation of audiology services in the West.
"We always felt the mechanism used by the HSE wouldn't identify all children affected and so we're now calling on the minister to show leadership and establish an independent investigation so the public can be reassured they have a service that is fit for purpose and so that we can make sure no other children are out there," Mr Corcoran said.
Additional reporting Aisling Kenny