The Harper government insisted Wednesday that Ferguson was chosen on merit and that he's already taking French lessons.
But New Democrat, Liberal and Bloc Quebecois MPs said that's not good enough.
Moreover, they accused the government of misleading them about Ferguson's linguistic abilities when it sought opposition approval for the nomination.
Opposition parties can't block Ferguson's nomination but they made it clear there'll be no warm welcome for the new watchdog — a figure normally beloved by opposition MPs for exposing wasteful spending by the government.
Interim Liberal leader Bob Rae said the government's job posting listed bilingualism as an essential qualification for the next auditor general. Yet, when the government advised opposition parties of its choice, it did not reveal that Ferguson didn't meet that criteria.
"For the last 20 years, the auditor general of Canada has been bilingual," Rae told the House of Commons, noting that all other independent officers of Parliament also have "a working capacity in both languages."
Immigration Minister Jason Kenney, answering for the government, said bilingual candidates were sought and, after an "exhaustive" search, "the most meritorious candidate" was chosen.
Kenney added that Ferguson, currently New Brunswick's auditor general, has promised to become "proficient" in French and has already begun lessons.
Rae labelled Kenney's response "ludicrous."
"Is it the position of the government that there is no competent, qualified and fully meritorious candidate in this country, in this entire country, who is bilingual?"
The issue also arose in the Senate, where Government Leader Marjory LeBreton acknowledged there was "some discrepancy between the (job) notice and what was actually required by the government for this position."
She promised to look into the matter.
New Democrat MP Yvon Godin held out little hope that Ferguson will learn French now, after failing to do so while serving as auditor general in the country's only officially bilingual province.
"He was four years in New Brunswick as a AG and he never did learn French in four years. Is he saying in the next four years he's going to be bilingual? Give me a break," Godin said.
He said the appointment means the auditor general will not be able to communicate his findings to Quebecers or francophones in other parts of the country.
Rae said the government had an obligation to ensure the auditor general is someone "who can communicate strongly, clearly, emphatically in both official languages."