Mr Ahern is the first senior figure from the Irish government to admit that it looked like the treaty had failed.
“It looks like this will be a No vote,” Mr Ahern said on live television. “At the end of the day, for a myriad of reasons, the people have spoken.”
He said it looked like other EU countries would ratify the treaty, so an Irish No vote would leave the EU in “unchartered waters”.
The BBC, Irish minister says EU vote lost