Mulcair was asked on Friday for his thoughts on the internal turmoil that has rocked Manitoba's governing party, with a number of members suggesting that Selinger step down.
Selinger has refused to resign, but he recently welcomed a leadership vote that is expected to be held at the provincial NDP's annual convention in March.
"Well, of course the premier has my support, and there is a process in place to let the members of the party review that in the new year," said Mulcair, who is in Winnipeg for a child-care conference.
"I have occasion to talk to him recently and he has my support."
On Thursday afternoon, Selinger announced that five former cabinet ministers who openly questioned his leadership would remain in the NDP caucus for the time being.
The high-ranking former ministers, known informally as the "Gang of Five," are:- Jennifer Howard, Fort Rouge, former minister of finance.
- Stan Struthers, Dauphin, former minister of municipal government.
- Theresa Oswald, Seine River, former minister for jobs and the economy.
- Andrew Swan, Minto, former minister of justice.
- Erin Selby, Southdale, former minister of health.
Backbencher MLA Clarence Pettersen, who also called on Selinger to resign, is allowed to stay in caucus as well.
'Not a lot surprises me anymore,' says Melnick
And longtime NDP MLA Christine Melnick, who had been sitting as an Independent since she was kicked out of caucus in February, is being brought back in.
On Friday, Melnick told CBC News she didn't know of the decision until shortly before it was announced.
"Not a lot surprises me anymore," she said.
"I would say I was made aware just before the meeting, which is what happens, and I have yet to discuss details with what the decision actually is."
However, the MLAs' role as caucus members has been severely limited. They cannot attend caucus meetings and they have no say in decision-making.
Melnick said even though it appears she's being treated the same as the Gang of Five, there is a difference between her and them.
"Their actions were very different than my actions so I feel there's a differentiation," she said.
"But to me … I'm a New Democrat, I always have been, always will be, and those sorts of discussions would be more internal than external."
In allowing Melnick back into the NDP caucus, Selinger said he "wanted to treat everyone equitably."
Melnick said she has always voted with the NDP, even when she sat as an Independent.