The new Official Opposition leader said he won't immediately be making drastic changes to his NDP caucus, but he does intend on shaking up the Canadian political landscape.
"You're going to understand how it's important for us to be able to project confidence and competence as public administrators," Mulcair said during his first news conference Sunday.
"That's sometimes what was missing."
Mulcair, who was elected Saturday to succeed the late Jack Layton, insisted the NDP is united after the long leadership campaign but must stay focused on the job ahead.
"We're facing a government that's very tough, very well structured and we've got to do the same thing," Mulcair said.
He added New Democrats must reach out to more voters, especially young people.
"We are the only party that can stand up to Stephen Harper and form the government in 2015," he said, adding that the next election will offer voters "a very stark choice" between the Conservatives and NDP.