The Liberal premier issued a brief statement saying Glennie Langille's 30-year career as a journalist made her qualified for the post.
McNeil's office confirmed that other people had applied for the job, but a competition was never held.
"No rules were broken in appointing Ms. Langille," McNeil's statement says. "(The cabinet) has the ability to hire people for certain jobs without holding a competition."
Soon after the appointment was announced in December, McNeil said the cabinet had asked Langille — his former communications director — to take the job ahead of other applicants because she was qualified for the position.
Since then, the opposition has accused McNeil of engaging in pork-barrel politics.
Langille has declined repeated requests for interviews.
On Thursday, the NDP released a series of internal emails that the party says raise questions about Langille's qualifications and the lack of an open and transparent hiring process.
NDP Leader Maureen MacDonald said it remains unclear whether anyone else was considered for the job. As well, she said the emails, obtained under the Freedom of Information Act, make no mention of other potential candidates.
"This isn't a job that should be filled in a political way," said MacDonald. "This is a function of government on behalf of the province. It's not a political staff position. ... It's a public position paid out of public funds."
MacDonald cited an email from Langille to McNeil's chief of staff, Kirby McVicar. In it, Langille says her resume has to be changed because "I really don't think it works for the purpose you requested."
Donald Savoie, a professor at the University of Moncton and one of Canada's leading experts on public policy, said McNeil's assertion that no rules were broken misses the point.
"Legally required or not, the question is, why wouldn't you hold a competition?" said Savoie, who has served as adviser to several federal and provincial governments, the United Nations and World Bank. "In the age of transparency that we live in, it's best to hold a competition."
Conservative Leader Jamie Baillie has said the job should have been filled through a competition under the government's fair hiring policy, arguing the protocol officer's position is not exempt from it.
"It proves what we were saying all along, that it was a blatant patronage appointment," said Baillie in an interview on Friday.
A spokesman for the premier disputes the assertion that the fair hiring policy applied to this case, saying the list of exemptions is not exclusive to those listed on a government website used by the opposition parties to make their argument.
Langille, who finished third in the riding of Pictou West when she ran in the October election, is being paid about $85,000 a year through a year-to-year contract.
"This is not a permanent civil service position and no future government will be bound to this hire," McNeil's statement says.
The chief protocol officer co-ordinates official ceremonies and events, including visits from the Royal Family, ambassadors and heads of state. The office also manages the Order of Nova Scotia and consults with government departments, non-government organizations and the public.
Last month, the Liberal majority on the legislature's human resources committee blocked an NDP request to have the protocol office answer questions about the appointment.
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