Erik Millett has been on medical leave since the debate over his decision to cut back on the singing of O'Canada at the school where he was principal. (CBC)

The elementary school principal who sparked a national debate by cutting back on the singing of the national anthem at his New Brunswick school has resigned.

Erik Millett has been on medical leave since becoming embroiled in the debate over his decision to allow the anthem to be sung only on special occasions at Belleisle Elementary School in Springfield, north of Saint John.

Millett told CBC News in February he became the target of nasty messages including death threats following the decision to eliminate daily singing of O Canada.

Police are investigating the death threats among thousands of emails and phone calls he received.

In February, Millett said he was seeing a psychologist as he attempted to overcome the backlash over the anthem dispute.

"It's pretty traumatic. I just hope that no teacher, no administrator has to go through something like that again," he said.

Singing now mandatory in all N.B. schools

Some of New Brunswick's Conservative MPs even attacked his decision on the floor of the House of Commons as "political correctness run wild." Eventually, the district superintendent ordered that daily singing of the anthem be restored.

Following that, the provincial education minister, Kelly Lamrock, made singing the anthem mandatory in all New Brunswick schools.

"In the end I think the policy is right. I certainly wouldn't comment on personnel matters, except to say that I wish Erik Millett all the best. And, in this particular matter, I think that we got the policy right, and I hope that the principal is able to continue his career as an educator," Lamrock said Wednesday.

Millett has said he made the original decision because two parents objected to the anthem ritual on religious grounds, and that he and his staff took the necessary steps to foster an inclusive school.

The superintendent of School District 6, Zoe Watson, said Wednesday she is looking for a new principal to replace Millett.

She said Millet plans to return to teaching.