He pointed out that there is no mention of the treaty in the Programme for Government, and said the Greens had signed up the programme and would honour it.
A special party convention is to be held in Dublin on 19 January next to decide the Green position on the Reform Treaty. All paid-up members of the party will have a vote on whether to support the Treaty.
The spokesperson said it had not yet been decided if the party leadership would advise members which way to vote.
The comments follow today's Cabinet meeting, which gave authority to the Taoiseach and the Minister for Foreign Affairs to sign the treaty at a summit in Lisbon tomorrow week.
The treaty will be the subject of a referendum next year - Ireland is the only EU country whose citizens are to vote on it.
