She says the issue is no longer "in some far away, distant time"
Sinn Féin deputy leader Mary Lou McDonald says the British exit from the European Union has given us the perfect opportunity to look for a united Ireland.
She says the border with the North is blocking our economic growth, and we need to remove it to improve our finances.
The party is continuing its planning meeting in the City North Hotel in Meath.
"The important thing is that Sinn Féin as a political party is, and remains, and increasingly grows and grows as a vehicle for progressive politics, for working people, working families north and south," she told the Pat Kenny Show here on Newstalk.
"On paper and rhetorically, each of the large establishment political parties will tell you that yes they favour Irish unity - that's their position on paper.
"I think what has changed now - perhaps not least because of Brexit - is that the Taoiseach, indeed the leader of Fianna Fáil, were forced into a position to concede that actually Irish unity and the issue of the border has to be considered now (and) not in some far away, distant time."
Asked about the added cost to the Republic in the case of a united Ireland, Ms McDonald replied: "It is virtually impossible to get a definite figure from London.
And secondly sometimes when these things are discussed you'd imagine nobody in the north of Ireland pays a schilling in tax - and that indeed none of the corporations or businesses pay a schilling in tax."
"You're asking can we afford unity? I put a different question to you: can we afford not to have unity?
"The border is a huge impediment, it's actually a liability for us.
"Research has actually shown that reunification would result in a very, very significant boost to the Irish economy."