Martin's comments come after Northern Ireland Office Minister Steve Baker suggested that a "super-majority" might be needed for such a vote to succeed, instead of the current requirement of a simple majority (50% plus one).
Martin emphasized the importance of respecting the constitutional changes endorsed by the people of Ireland, as laid out in the 1998 Good Friday peace agreement.
Baker's suggestion faced criticism from various quarters but has since been played down by Northern Ireland Secretary Chris Heaton-Harris, who clarified it did not indicate a change in government policy.