The Comptroller & Auditor General has described a figure of 8% in overpayments of job seekers allowances as "high".
In its annual report, it acknowledged the Department of Social Protection has taken steps to address risks of overpayment.
The job seekers allowance scheme cost the State €1.5 billion in 2021.
The Department's own survey also found a 1.4% overpayment of child benefit was paid out last year, which was an increase on the 0.5% overpayment figure found in the Department's 2013 survey.
The child benefit scheme cost just over €2 billion last year.
The C&AG report has described the level of irregular payments found by the Department as "material".
The report cautioned how even small levels of excess welfare payments can amount to significant losses of public funds.
It notds how the Department of Social Protection's expenditure increased by more than 50% to over €31 billion due to the Covid-19 pandemic.