Special licensing exemptions, which allow nightclubs to serve alcohol after normal closing hours, are being abused by some members of the trade, the Taoiseach has said.
He was speaking after it emerged that gardaí are likely to object in court to the granting of late licences because of public order issues.
Mr Ahern said that while he could see the sense in premises opening late on a Saturday, opening until "the late hours of the morning" was not what was intended in liquor licensing legislation.
"There are several places that seem to be open not until the early hours of the morning, but the late hours of the morning. I don't think that was ever the intention."
He had been informed by young people that there was no difficulty getting alcohol in Dublin at "four, five and six o'clock on a Sunday morning . . . I don't remember ever passing that Act, and I don't think it's a good thing either."
Nightclubs operate under the same licensing restrictions as public houses, but can seek exemption orders allowing them to open to 4.30 a.m. in some cases.
Mr Ahern added that he was "not a spoil sport", but said people were abusing the system.
He could see that it was not a good idea to have everyone leaving licensed premises at the exact same time because it caused public order problems and difficulties for people trying to get taxis.
He said that these were issues that would have to be worked out in the review of the licensing laws.
The Labour leader, Mr Pat Rabbitte, said moves by senior gardaí to force nightclubs to close earlier than usual have arisen because manpower shortages within the Garda were so acute.
"It is an adult city. I don't think prohibitive measures like these are going to be successful or desirable.
"Some viable presence of gardaí is the place to start. I think the public would be generally shocked if they knew the amount of gardaí in any given station in any given night.
"We've abandoned the notion of gardaí on the beat. We have a problem. It will only lead to a situation where people will imbibe at an even faster rate, and they will come out onto the street at the same time."
It is expected gardaí will begin objecting to the exemptions from tomorrow.
Mr Robbie Fox, who owns Renards nightclub in Dublin and is a spokesman for the Irish Nightclub Industry Association, said that the move would result in 30,000 drinkers being let out into Dublin's streets all at the same time.
"It's common sense that if you put people on the streets at a slower rate you will take the pressure off the streets.
"We did a survey last year and there were six or seven gardaí on duty in Galway city on one night and in one nightclub there were 30 doormen on duty. That makes no sense at all.
"There was one other town where we found the same amount of gardaí on duty on a Saturday night as on a Monday morning."
"We've met the Minister for Justice, and he said in the new year there will be a codification of licensing laws, and that all these things will be addressed.
"If this passes on Wednesday we will be out of business."
He said any move which forced venues to close early would cost jobs.