Dexter's NDP government has come under fire for its decision to change the terms of reference for the independent, eight-member Electoral Boundaries Commission.
Opposition critics say the changes will lead to the elimination of three ridings that are considered protected for Acadians, and one that has a significant black population.
But Dexter said Thursday the commission's terms of reference make it clear it has to recognize "communities of interest" when redrawing electoral districts.
"The terms of reference, they directly reference those communities and they empower the committee to take those things into account," the premier said after a cabinet meeting.
He said the changes were proposed weeks ago, but the opposition did not raise any objections until the last minute, just as a select legislative committee was wrapping up its work last Friday.
The committee was presented with nine different drafts of the terms of reference, but the opposition had little to say about them, Dexter said.
"They never once took issue with that change," he said. "This is a fair, open process that is completely transparent."
The opposition Liberals and Tories have also complained that the NDP-dominated committee that approved the changes did so after a series of closed-door meetings — an allegation the premier denied.
NDP cabinet minister Percy Paris, a black member of the legislature, said he was confident "diversity would be given a top priority" by the commission.
When asked if he thought the Halifax-area riding of Preston had outlived its usefulness to the local black community, he said: "One of the goals of the Preston riding was to ensure, to some degree, that an individual of African descent had a fair chance and hopefully would represent the riding ... Well how good is that working?"
Paris went on to note that the riding has been represented by black politicians in the past, but it has had a white member, Keith Colwell, since 2003.