A Yes vote in the Nice referendum will be a vote for jobs, economic growth and security of Ireland's future, the Taoiseach has told a Dáil.
"Ireland should show the way and not block the way," Mr Ahern said in a parliamentary debate on the issue.
He said a Yes vote would ensure continued foreign direct investment and would maintain and open up European export markets, with 100 million new customers for Irish business.
He said Ireland had benefited more than any other state from the European Union and other countries seeking entry should not be denied the same opportunity.
"It is not right to deny the opportunity for a better life for so many of our fellow Europeans."
Mr Ahern dismissed claims from the No side that Ireland would lose its influence if the Nice Treaty was ratified by Ireland saying the argument was "a red herring."
"It will establish for first time equality among member states," he said.
He also said fears of a wave of immigration from poorer states was "simply not true."
"Surely we do not want to build a wall around this island." The Fine Gael leader Mr Enda Kenny said Ireland's association with Europe had boosted the country's influence "socially politically and economically."
"We need Europe as much as we needed it before and it needs us," he told the house.
"This Government was elected on a platform of gross deception. The people are sore. I would ask them to remember that YES to Nice is not a vote for the Government. It's Yes for a strong economy, Yes for equality, Yes for new opportunity, Yes for a secure future.
"Yes is a vote for Ireland, not for the Coalition."
"The eyes of the world are upon us there is no plan B," he added.
