Mulcair began campaigning with NDP Leader Dominic Cardy in Fredericton as the race to Monday's election entered its final days.
Cardy has promised to wait two years before considering development of a shale gas sector, at which point companies wanting to exploit the resource would have to undergo tests to assure health and environmental concerns are satisfied.
"Dominic has my full backing on the position he has taken on fracking," Mulcair said.
"It's a clear position that everyone in New Brunswick can understand, and it's two-fold ... he's talking both about the procedure of fracking and the fact that it won't bring anything into the coffers of the province."
Mulcair said he supports a shale gas industry but is against the process of hydraulic fracturing or fracking, which involves pumping large volumes of water and chemicals into a well in order to fracture layers of shale rock and release trapped pockets of gas.
"It's not the substance that's the problem, it's how you're trying to get to it that's the problem, and this is not a method that is safe," he said.
Cardy has also committed to setting up a royalty rate and putting shale gas development to a free vote.
Shale gas has been a divisive issue in the campaign, with the Liberals saying they would implement a moratorium while the governing Progressive Conservatives promoting it as a way to stimulate the economy.
Two other federal leaders — Justin Trudeau of the Liberals and Green Leader Elizabeth May — have also campaigned alongside their provincial counterparts since the campaign began a month ago.
Liberal Leader Brian Gallant stuck to his jobs message on Friday and attacked Progressive Conservative Premier David Alward's record on employment.
The Liberal plan for infrastructure spending will create more than 1,700 jobs, he said.
"We need a government that puts jobs first and that is what we're offering," he said in a statement.
Alward reiterated his position on shale gas, saying development of the industry will generate $10 billion in private sector investment and create jobs across the province.
"The choice is clear," Alward said in a news release. "New Brunswick is on the verge of seizing the opportunities ahead, and the Progressive Conservative team is the only party with a plan to bring our people home and create opportunities for future."
Green Leader David Coon, meanwhile, promised to consult First Nations on resource development to comply with a recent Supreme Court of Canada decision. The Greens support legislation, he said, making it the government's duty to consult with Aboriginal Peoples.
Cardy was asked again Friday about an Internet video that surfaced a day earlier that had been retweeted by a couple of NDP candidates.
The tweet linked to a video parody from a film about the final days of the Nazis. It shows senior members of Adolf Hitler's inner circle discussing their fate as the Allies are close to winning the Second World War.
The parody depicts the actors as senior Liberals through subtitles on the screen, a depiction that Gallant found offensive.
On Thursday, Cardy said while he was disappointed in his candidates' behaviour and asked them to remove the video, he was also disappointed at Gallant's reaction, calling it a campaign stunt.
Less than 24 hours later, Cardy was more apologetic.
"I absolutely, unreservedly apologize for any offence that anyone took from the actions of the NDP as a result of the videos," he said.
"They had nothing to do with the NDP, they were just being reposted, but that doesn't take away from the lack of judgement involved in reposting them."