At least 300 people will be refused a Private Security Authority (PSA)licence to work as door supervisors or security guards in the coming weeks, mainly due to concerns about previous criminal convictions.
However, the final figure could be significantly higher, as only about half of some 20,000 applications have so far been fully processed, including vetting by An Garda Síochána.
In an interview with The Irish Times, PSA chief executive Geraldine Larkin said she was also aware of at least one case where an individual would be refused a licence because of a rape conviction.
However, she said she could not say that a conviction for rape would automatically disqualify someone from having a licence. She said the authority would have to take into account the judgment of the courts in a particular case.
"I can't categorically say to you that I will refuse all convictions for rape," Ms Larkin added.
The PSA assesses each application for a licence on a "case by case" basis, she said, while also noting that a decision by her organisation to refuse an application could be subject to an appeal.
"It's very difficult to take a one strike and you're out approach because this could potentially be a person's livelihood . . . and if you argue that they've done their time and that there's been no criminality since, that person is entitled to a chance, to an opportunity."
Approximately half of refusals to issue a licence are due to a previous conviction for assault or theft, while in a further 30 per cent of cases, the individual has a previous conviction for a drugs-related offence.
In a revelation likely to prompt some concern, the PSA, which is overseeing reforms in the operation of the private security sector, also believes the vast majority of those whom it has deemed unfit to hold a licence are working in the industry.
They are employed either as "static" security guards, typically in retail stores, office complexes, industrial estates and on building sites, or as door supervisors or "bouncers" in pubs and nightclubs.
It is also thought that as many as 5,000 others have not yet applied for a licence, prompting suggestions that many within this group may not be doing so because they know their previous criminal record would lead to a refusal.
The authority has previously revealed that almost one in 10 applicants had a conviction, but that the majority of these - for example convictions for minor road traffic offences - are not deemed relevant to their application.
Applicants may be refused for other reasons, such as failure to provide the relevant training documentation and failure to provide a criminal record certificate from a foreign jurisdiction.
The authority says it has started issuing the first batch of approximately 4,000 licences over the Christmas period and will start issuing notices of refusal in the coming weeks.
Since last April it has been an offence to operate in a designated sector of the private security industry without a licence. It is also an offence to employ an unlicensed person. The PSA also said that as many as 70 per cent of applications were incorrectly filled out.