DUBLIN - The British government has a "democratic imperative" to call a referendum on whether Northern Ireland should leave the United Kingdom and unite with the Irish Republic, the province's Irish nationalist Deputy First Minister said on Friday.

"The British government now has no democratic mandate to represent the views of the North in any future negotiations with the European Union and I do believe that there is a democratic imperative for a 'border poll' to be held," Sinn Fein's Martin McGuinness told national Irish broadcaster RTE.

"We are now in unchartered waters, nobody really knows what is going to happen. The implications for all of us on the island of Ireland are absolutely massive. This could have very profound implications for our economy (in Northern Ireland)."