A Bank of Ireland branch in Dublin earmarked for closure is used by 220 people per hour, the Financial Services Union has claimed.
The union also said that three quarters of all branches the bank intends to shut here have at least 500 visitors a week, with one quarter having between 1,500 and 3,000 visiting every seven days.
The FSU claimed the data it has seen shows that the lender needs to publish the complete footfall numbers for every branch that it intends shutting later this year.
Last month, Bank of Ireland said it would close 88 branches in the Republic of Ireland due to falling footfall as a result of changing banking habits.
"Bank of Ireland have led us all to believe that footfall in these branches was non-existent and that the branches were empty most of the time," said John O'Connell, FSU general secretary.
"These numbers show that even in the middle of a pandemic and where the branch is only open part time people are regularly using their local bank branch."
Mr O'Connell added that the information shows that contrary to what it has claimed, the bank's decision is actually motivated by cost-cutting and increasing profits.
He also called for the Central Bank and Minister for Finance to intervene to push Bank of Ireland to review their decision and pause the closures until the pandemic is over and a debate has taken place on the future of the sector here.
At a recent Oireachtas Committee hearing, Bank of Ireland chief executive, Francesca McDonagh said the lender will not be reassessing its decision to close the 88 branches in the Republic of Ireland.
She said the decision had not been taken lightly and added that the bank had looked over a long period of time, even before the Covid-19 pandemic, at customer behaviours and preference.
Ms McDonagh said that of all the 88 branches closing three out of four customers using them haven't set foot in one in the last 12 months.
"We are not in the business of closing busy branches," she stated.
"We are responding to a shift in customer behaviour."
She added that the shift to digital is permanent and established.