Varadkar has it easy with FF backing him, says Bertie
Fianna Fáil should end deal after three years - ex-Taoiseach
Mr Ahern claimed he had a tougher time when he had to rely on a motley crew of Independents such as "Jackie Healy-Rae and Mildred Fox and a few of them to get things done".
He said the Government was riding high in the polls because of Fianna Fáil but the time is approaching to "move on" from the confidence and supply agreement. As soon as the three-year term is complete, there should be a general election.
Mr Varadkar is "in a great position at the moment where he has the support of Fianna Fáil", Mr Ahern told the Irish Independent.
"I had to depend on Jackie Healy-Rae and Mildred Fox and a few of them to get things done", but Mr Varadkar can "rely on Fianna Fáil" for "95pc of issues".
Fine Gael's approval rating has been consistent for the past few months and the party is reaping the rewards of relative political stability.
This, alongside Mr Varadkar's high personal rating, has been compared with the days when Mr Ahern's popularity was at its peak. Asked if he thought Fianna Fáil had regained the trust of the people since the economic crash, he said: "Yeah, I think it has, but it is not back to where we were."
"I used to feel upset if we didn't get over 38pc in the polls," he added.
Fianna Fáil is currently on around 28pc, according to the 'Sunday Independent' poll from February. But Mr Ahern acknowledges that the confidence and supply agreement was the best plan for the country at the time.
"I agreed with Micheál Martin," he said, that the party was right to support the formation of a Government, "the country needed it".
He added: "I think Fianna Fáil has got some credit for the confidence and supply agreement, it is due credit; but it has to move on when the three years are up.
"When the Budget finishes and the social welfare bill and the finance bill go through in the new year, that's it. It has done its bit and should move on."
Mr Ahern predicts there will be a general election around this time next year.
"Politicians don't like winter, and neither do voters, so it will have to be around this time next year."
The European elections and the local elections are due to take place in May 2019. It's possible to have them all on the same day or very close together, said the former Fianna Fáil leader.
In Northern Ireland, Assembly elections took place one month and European elections the following month, he said. So, "you could do one in April, one in May, or the same day".
Mr Varadkar entered politics in 2007, just as things were beginning to fall apart for the Fianna Fáil government.
During the brief spell in which they encountered each other as TDs, the then-Taoiseach predicted Mr Varadkar would "get an early exit".
Mr Varadkar had been particularly disparaging of Mr Ahern over his controversy relating to personal finances, telling the Dáil: "This dark affair will darken the Taoiseach's record in the same way as Tony Blair's involvement in Iraq or Bill Clinton's personal scandals darkened theirs".
Now, Mr Ahern says Mr Varadkar is "a bright guy, and doing OK", but the big tests are all ahead with Brexit and the North.