Premier David Alward announced Wednesday that Margaret-Ann Blaney would head the Crown corporation, which is mandated to promote efficient energy measures.
Alward says Blaney is the best person for the job, which pays an annual salary ranging from $150,000 to $170,000 and has no term limit.
"I have full confidence that I have the best person for the job and I have full confidence in the important role she will play going forward," Alward said.
But Liberal Opposition Leader Victor Boudreau said Alward should have advertised for the position.
"If he wanted to fill the position of CEO of Efficiency New Brunswick, he should have had an open competition."
NDP Leader Dominic Cardy called Blaney's appointment a "clear case of patronage."
"Maybe Margaret-Ann Blaney is exactly the right person to head Efficiency New Brunswick, but it would have been nice to have an internationally advertised position, the same way we used to do for civil service positions at this level back in the '70s," he said.
Blaney said her new job will allow her to continue serving the public while balancing her personal life.
"I will serve in a very professional role, serving New Brunswickers in a different capacity, but one that will allow for me to have that balance with family life and work life," she said.
She said it has been difficult to maintain that balance since a divorce about 18 months ago, adding that she looks forward to spending more time at home with her two teenaged children.
Blaney was first elected to the provincial legislature in 1999 and represents the Saint John-area riding of Rothesay. She will step down May 25 and begin her new job June 4.
The government must call a byelection within six months, and Alward said it would be soon.
"I don't believe communities should go long periods of time without representation by an MLA," he said.
"We'll make that decision in the coming days."
Boudreau said it was too soon to say if any of the four candidates for the Liberal leadership will seek the Rothesay seat. The Liberal leadership convention is set for the end of October.
But Boudreau is encouraging Cardy to seek a seat in the legislature. The NDP have no elected members in the province.
"This is an opportunity for him to show what he's made of," Boudreau said.
Cardy wouldn't commit to entering the race, but said the party would field a candidate.