The Sinn Fein president is calling for a border poll to be held in the next term of the Northern Assembly and Oireachtas.
Gerry Adams was speaking this afternoon at the launch of his party's campaign on the issue, in Dublin.
He says the the Good Friday Agreement, allows for a referendum in the North on a united Ireland.
Census figures published last month revealed that 40 per cent of people in the North considered themselves British.
The Louth TD says this suggests the political and demographic landscape is changing.
Deputy Adams says it is time for the people voice their opinion on unity: