The Lisbon Treaty will strengthen individual rights and those of Irish citizens at home, Labour Leader Eamon Gilmore has said.
Speaking at the launch of the party's campaign for a Yes vote, Mr Gilmore said the treaty provided for greater openness and accountability to European decision-making.
It provided, for the first time, a clear legal basis for European laws to protect public services, he added.
Mr Gilmore cautioned that support for the treaty should not be taken for granted.
Labour will spend €200,000 on a nationwide campaign including leaflets and outdoor billboards.
Meanwhile Sinn Féin has said the No campaign in the Lisbon Treaty referendum is not a lost cause.
MEP Mary Lou McDonald said Sinn Féin will intensify its campaign against the Treaty over the coming weeks.
She was responding to today's Red C poll in The Sunday Business Post, showing a 10% lead for supporters of the Treaty.
The poll reveals a shift back to the Yes side in the past two weeks, with support up three points at 38%.
Support for the No camp is at 28%, down three points.
Just over one third of voters remain undecided.
A fortnight ago, the Yes lead was 4%, but this latest poll puts it at 10%.
Yesterday, the Taoiseach, Brian Cowen, said that securing a Yes vote is the priority for his Government.