Former deputy prime minister Barnaby Joyce kicked off a media campaign on Wednesday, using an opinion piece and TV appearances to claim the Coalition was a "marriage of convenience".

Mr Joyce told Sky News that the Nationals should have a fifth cabinet position and accused Mr McCormack of going soft in meetings with Prime Minister Scott Morrison "because he doesn't want the aggro".

Mr McCormack retained his position as Deputy Prime Minister during a leadership spill in early February last year when Mr Joyce sought to reclaim his previous role in the party after an affair with a former staff member.

When asked by reporters about Mr Joyce's comments on Wednesday, Mr McCormack said the Coalition was "actually a marriage of strengths".

"The people out in the regions are relying on us for their jobs, for their futures, for water infrastructure, for road and rail. And that's what my focus is on," Mr McCormack said.

"They're not worried about the power struggles in Canberra. They're not worried about who might sit on a committee or what percentage of this and that is made up of the government. That hasn't even been raised with me before today."

In an opinion piece for The Australian newspaper, Mr Joyce said he had commissioned research from the Parliamentary Library that showed "Nationals cabinet ministers share responsibility for merely 3.45 per cent of the total federal budget".

Mr McCormack said his "whole sole focus" was on "building back Australia from the COVID recession, making sure that we've got the jobs for their families and their future and making sure that we roll out the infrastructure whether it's in Canberra or whether it's in one of those little one-horse towns that are so important, particularly to me as the Nationals leader".