AIB, the country's second-largest bank, has told financial regulator Matthew Elderfield it cannot implement his new 'fit and proper' rules for bankers by the deadline this September.
The bank is claiming that Mr Elderfield's plans, as drafted, could mean 10,000 AIB staff would be caught in the net of the 'fit and proper' test, which involves making sure bankers are qualified and trustworthy.
The bank has also claimed Mr Elderfield's plans are too heavy handed and could result in ordinary staff being vetted under the rules.
"It will, for example, capture those individuals who simply provide brochures to customers," the bank claimed in a letter to the Central Bank.
Mr Elderfield has been given new powers under the Central Bank Reform Act 2010 to vet bankers for their fitness and probity.
AIB's general manager Philip Brennan indicated in the letter that bringing in such rules by this September was unlikely to happen.
"Given the number of staff potentially covered in an organisation the size of AIB, it will be extremely challenging, if not impossible, to meet the September 1 deadline," he wrote.
But the bank's core argument is that the rules are going to end up covering staff who are not advising customers or who are not in a senior position.
The scope of what the regulator intended to do was far broader than previous attempts in this area, the bank said.
"The definition captures all members of staff dealing in or having control over the property of a customer. At the very least this should be restricted to those individuals who have discretionary authority over customer investments," stated the bank.
The bank argues that the way the rules are expected to be implemented means that more than 10,000 staff could be caught up in the fitness and probity tests.
The bank has also raised concerns about the appeal mechanism available for more junior staff if they are suspended or prohibited from working in a particular role.
UIster Bank, meanwhile, has also expressed concern at the scope of the fit and proper regime.
"We believe the scope as drafted is too wide and could capture an unnecessarily vast population of frontline, customer-facing processors," it said.
"A more selected approach would be preferred, focusing on roles which are sufficiently senior to influence policy, rules and decisions."
Ulster Bank also said the timeline for the changes may not be possible to meet.