BUS Éireann has come under fire after a number of scheduled buses were cancelled last Friday.
However, management say that fewer than 1% of scheduled buses were affected by the last-minute cancellations.
Overall, 17 services were affected by the enforcement of the 48-hour Working Rule, which limits the number of hours that drivers are allowed to work over the course of a week.
However, most of these services were covered by contractors, with just four scheduled services cancelled, according to Martin Walsh, regional manager for Bus Éireann South.
Mr Walsh said that while any cancellation is 'regrettable', fewer than 1% of all scheduled services were affected.
He denied that hundreds of passengers were left stranded, as had been suggested by critics.
"17 buses were affected; that is correct," he said.
"11 of these were covered by contractors, which is a normal policy we employ every day of the week. We missed out on two relief buses - these are not scheduled services but are deployed as and when they are needed - and we missed four short services; two to Kent Station, one to Cloghroe and one to Glenthorn.
"Of course, we deeply regret any inconvenience caused to passengers but drivers have to abide by employment legislation just like every other worker in the State."
SIPTU criticised management for the way the matter was handled.
Pat Hartnett, SIPTU rep in Cork, said there was 'no plan b' in action to ease the issues for customers.
"It's management's problem - they caused it by not allowing drivers to work more than 48 hours, but there was no plan b," he said.
"It's a sad situation for the passengers."
Solidarity TD Mick Barry criticised the last-minute changes.
The Cork North Central TD described it as 'utter incompetence' by management at Bus Éireann to enforce the 48-hour Working Rule.
"A child could have told them that the crude implementation of this measure had the potential to cause havoc," he said.
"The new national management have no background or experience in running a bus company and the reality is that they shouldn't have been let near one in the first place."
Mr Walsh rejected the notion that Bus Éireann was operating with 'no plan b'.
"Our plan b was operating," he said.
"We had 11 services covered by contractors. We use our fleet to its absolute maximum and we understand the importance of reliability."
He said that Bus Éireann is working hard to improve reliability in Cork.
"In the last three years, since I took over my role, we have hired more than 100 drivers and have added new buses to the fleet to ensure it is more reliable.
"Four services were missed and that is regrettable. We don't want to miss any services but it is less than 1% of the departures scheduled for Parnell Place on the day and we are bound by employment legislation just like everyone else.
"We carry more than 40,000 passengers every day in Cork and, for the most part, we receive favourable reviews and that is evident from a 25% increase in passenger numbers in recent years."