Sir Keir told The Yorkshire Post he would go further than the Prime Minister in handing powers and resources to metro mayors amid concerns that the Government is going cold on the devolution agenda.
It comes as a former Cabinet colleague of the PM warns today that he must develop his much-vaunted ‘levelling up’ agenda on a cross-party basis to avoid it floundering.
Justine Greening, who now heads the Social Mobility Pledge coalition of businesses and universities, also says Mr Johnson must be far more specific on his policy intentions.
The Prime Minister recently claimed devolution had been a disaster in Scotland and the promised White Paper setting out the Government's vision for creating powerful local mayors has been delayed several times.
And in North Yorkshire, where councils have been told to radically reform local government to get the benefits of devolution, Ryedale council leader Keane Duncan said he was also concerned about the PM's commitment to the agenda as government struggles for bandwidth during the pandemic.
On a visit to Yorkshire this week, Sir Keir said: "They're in a mess. Look at the North Yorkshire proposals, it's complete chaos now. And I don't think the Prime Minister's heart is in it. When he says devolution is a disaster, that's because he doesn't believe in devolution.
"And I think that the pandemic has actually proven the case for devolution, because where local leaders have been able to get a grip of a situation, they've done a much better job than the Government's done.
"I want decisions about people to be made as close to them as it can be. And I have believed that for a long time for the four nations, but I think the regions themselves now need more power, they need more resource."
Earlier this week, Greater Manchester metro mayor and former Labour Cabinet Minister Andy Burnham said the party needed to become more enthusiastic about devolution to get its own version of the Tories 'levelling-up' agenda.
Former Deputy Prime Minister Lord Heseltine also told a northern transport conference the Government had "lost interest" in the issue.
But North Yorkshire County Council leader Carl Les defended the Prime Minister and said he'd had a letter from him earlier this month confirming his commitment to handing powers from Whitehall.
His council and district leaders have presented rival visions for how local authorities can be reformed, with Communities Secretary Robert Jenrick due to make a decision in 2021.
Conservative Coun Les said: "We have two competing proposals, I don't think that is a complete mess. But I would rather we just had one proposal and that the districts had seen the wisdom of our arguments."
He said the frustration over devolution was caused by local leaders failing to agree, with two district councils refusing to approve the 'asks' from government if it were to get a metro mayor.
Ryedale council leader Keane Duncan said: “It is my sincere hope that we can secure a devolution deal for York and North Yorkshire, but I am sensing a lack of government confidence that one will ultimately be delivered."
The Conservative councillor said: "Is the Prime Minister’s heart still in Manchester-style devolution, if it ever was? Is he perhaps looking at other ways to deliver his ‘levelling up’ agenda to our neck of the woods? I don’t know.
"But with things less than certain, it’s right that we don’t blindly focus, as some are, on devolution. We need to ensure that we get the ongoing council reorganisation right for the long-term.
"We need responsive and effective new councils, that can work with or without a devolution deal. We must get that process right or the public will be paying the price for decades to come.”
And this week Chancellor Rishi Sunak, an MP in North Yorkshire, said rewiring how central government works and empowering local leaders was part of his vision for the Government's 'levelling up agenda'.
He spoke at a meeting of the Northern Powerhouse Partnership lobbying group, whose chairman, former Chancellor George Osborne, said: "I know from experience that the Treasury alone can’t build the northern powerhouse, but without the Treasury it is much harder for anyone else to - it’s by working together on things like skills, transport and jobs that we can make the whole greater than the individual parts."
On Wednesday an order turning West Yorkshire's landmark devolution deal into law next February was laid in Parliament.
A government spokesperson said: "Levelling up remains at the centre of the Government’s agenda and we are empowering all areas of the country by devolving money, resources and control away from Westminster, unleashing the potential of all our regions.
"On 9 December we received two locally led proposals from North Yorkshire councils for new unitary structures in the area, in response to the Secretary of State’s invitation, and ministers are now carefully considering these proposals."