Sinn Fein's Elisha McCallion has said it is up to people to make a decision over Irish unity and not the Northern Ireland Secretary or the Tory party "who have no mandate in Ireland".
Ms McCallion was speaking after James Brokenshire said people who vote for nationalist and republican parties in Northern Ireland do not necessarily support a united Ireland.
Mr Brokenshire made the comments as he launched the Conservatives' Northern Ireland manifesto at the Crowne Plaza hotel in Belfast.
McCallion said: "The Good Friday Agreement contains provision for a referendum on Irish unity and that cannot be wished away by James Brokenshire and his Tory colleagues.
"It will be up to the people of Ireland to decide their future not the man from Old Bexley and Sidcup and his Tory party who have no mandate in Ireland. His bizarre comments on Irish nationalist and republican voters beggar belief.
"In the recent Assembly election Sinn Féin received a huge mandate of more than 224,000 votes for our platform of equality, respect and integrity in the political institutions and for our support for Irish unity.
"Support for Irish unity is growing, a recent Lucidtalk opinion poll showed that a majority of people in the North are in favour of holding a referendum on Irish unity.
"Sinn Féin has called for a referendum on Irish unity to be held within the next five years. The outgoing Tory government has pandered to the DUP and political unionism since coming to office in 2010, James Brokenshire’s comments are simply more of the same nonsense."