Kildare voters should not leave the constituency without a Government representative, the Taoiseach, Mr Ahern, has said.
Formally launching the by-election campaigns of Kildare North's Ms Aine Brady and Meath's Mr Shane Cassells, Mr Ahern said FF would be "going all out to win".
Last week, the Minister for Finance, Mr Cowen, said Kildare North would lose out if Ms Brady failed to win in the March 11th by-election.
However, Mr Ahern rejected charges that FF was putting undue pressure on voters. "There are no threats in Fianna Fáil, you know that. It would be sad if Kildare North would be the only constituency in the country without a FF representative," he told the Shelbourne Hotel press launch.
Voters in Kildare would have occasions when they were "looking for somebody on a Monday night, and a Tuesday night, a Thursday night, a Friday night, and Saturday clinics, sporting events, religious events.
"Then it is good to have a representative. That is what all of us do. If you don't have a representative to do that you are disadvantaged. Brian is just pointing out the reality."
However, he emphasised that Fianna Fáil would face a major challenge to hold on to the Kildare seat once filled by Mr Charlie McCreevy, or to gain one in Meath. "It is just the reality. It requires people to work hard; a huge campaign and effort in a short period of time. But we have two superb candidates."
He said Fianna Fáil had worked hard under the leadership of its general secretary, Mr Sean Dorgan, to improve its organisation in the wake of last June's disappointing local election results.
"Organisationally, we have worked very hard. We have put in a huge amount of effort to building up party membership, getting them closer to the community.
"It is a problem of the larger parties that people think that (by-elections) can be fought out on a TV campaign. As much as TV and radio is important, I tell you it doesn't fix the local issues. In fact, it does nothing for local issues."
Questioned about a transfer pact with the PDs, he said the parties "hadn't discussed that".
"We haven't done that in recent years. We would hope that not only from PDs, but from other places too, that people would recognise good candidates."
He declined to criticise the Sinn Féin candidate in Meath, Cllr Joe Reilly.
"I did not say anything derogatory about any other candidate. I'm always glad to see people putting their names forward."