As Libertas chairman, Ganley is one of the most high profile opponents of the Lisbon Treaty, which Irish voters rejected last year amid a lack of information about the treaty and fears Dublin would lose control over policy areas such as tax.
Ganley, who helped fund Libertas' 'No' campaign, has said he wants the Parliament elections to be a European-wide referendum on the Lisbon Treaty.
"Declan has announced tonight that he's running in Ireland North West," the spokeswoman said.
The group, which describes itself as a pan-European political movement, is fielding parliamentary candidates in other countries, such as France.
Ireland will vote for a second time on the Lisbon treaty, which is meant to streamline decision-making in the 27-member bloc, later this year.
Dublin is hoping concessions given to Ireland by Brussels, including the right to retain its own commissioner, as well as assurances on taxation and neutrality, will smooth the treaty's passage.
Ganley, who describes himself and Libertas as pro-Europe, has said the treaty should be rejected because it is anti-democratic.
Recent opinion polls have shown Irish people voting in favour of Lisbon as a deepening recessions warms their views of Europe, seen as a buffer against an Icelandic-style bust.
No date has yet been set for a second referendum but it is expected to be held in the second half of this year. Brussels would like Ireland to ratify the treaty as soon as possible to give the EU a greater weight in world affairs, particularly during the current global economic turmoil.
Meanwhile, controversy over the party's funding and operation continues to dog Libertas. A report published last week by the Irish Standards in Public Office Commission (Sipoc) showed that Libertas failed to provide adequate information on its activities during last year's Lisbon Treaty referendum campaign.
Specifically, the Sipoc report claimed that details of a repayment plan for €200,000 that Declan Ganley personally loaned to the Libertas campaign had not been provided to their investigation.
Sipoc also revealed that it questioned Libertas on whether staff at Ganley's Rivada Networks – a telecommunications company which has a lucrative contract with the US military - may have been paid by that company while working for Libertas on its referendum campaign.
(EurActiv with Reuters)
