Speaking to LBC presenter Andrew Pierce about the devastating flooding which hit communities including Fishlake and Stainforth, Mr Mitchinson told the broadcaster: "In David Cameron’s memoirs he states that sometimes as Prime Minister you simply have to respond to what mother nature throws at you, and that was in his memoirs in relation to the floods he dealt with in 2014. Had Mr Johnson read Mr Cameron’s memoirs, there was a little nugget of advice in there for him..
"The people of Fishlake and Stainforth and right across South Yorkshire affected by these floods do not believe that the Prime Minister reacted quickly enough nor proportionately to the scale of the devastation.
"He should have been chairing a COBRA meeting immediately as soon as it became apparent how bad these floods were. He didn’t call a COBRA meeting, he told us - and we splashed it on our front page - that this is not an emergency, and we disagreed and have kept the pressure on ever since.
"Let’s just take the politics out of this, it’s not about the colours of the rosette, it’s about whether or not the person in charge of the country responded quickly enough and in the right way. And what we saw were pictures of him sloshing a mop around in a Specsavers in the Peak District… it just didn’t look good did it?"
The Prime Minister visited Matlock in Derbyshire after the area faced significant flooding following heavy rain that caused one death and many evacuations.
The visit came as extreme heavy rain left several South Yorkshire communities wading through floodwater.
Mr Mitchinson pointed out the Prime Minister's 'missed opportunity' and called for Boris Johnson to pledge match funding for the Community Foundation Floods Disaster Fund.
He continued: "Whoever is giving the Prime Minister advice, whoever’s in charge of his campaign… if I was Mr Johnson I’d be kicking him out and getting someone else in because this really was an opportunity for Mr Johnson on the campaign trail to live by his words.
"It was only a couple of weeks ago, your listeners will recall, the Prime Minister was standing on his hind legs and saying the Conservative party is a moderate party and it’s a compassionate party.
"He had a great opportunity to demonstrate compassion to the people of South Yorkshire and he missed what I think was an open goal. But that’s all gone, that’s in the past, he needs to now do something to make amends. I think he could start by match funding the Community Foundation Floods Disaster Fund which I think has now exceeded the £300,000 mark, and the Prime Minister would be wise to quickly declare that he’s prepared to match that fund and then some."
Mr Mitchinson also called for more to be done to help people in flooded communities struggling to get insurance cover, adding: "There are businesses and homes that can’t get insurance.
"We’re not talking about the Cotswolds here, they’re not million pound mansions, these are very nice houses but they cost something like £100,000 and the insurance companies want £10,000 a year to insure them, and people are making decisions based on whether or not they can afford to pay extortionate premiums. Somebody needs to get the insurance companies in hand because what they’re doing, frankly, is criminal.
“If I was the Prime Minister’s campaigner I’d have had him back here before now and I’d have had him here demonstrating in the form of an holistic strategy created alongside people who know best in the local emergency services, in the local authority, and I’d be here telling them - as we’ve heard in the other instances where there’s been flooding of this scale - I’d be saying ‘money is no object, and you can trust me folks to put this right for you and while I’m at it I’m going to have a word with these insurance companies and I’m going to find a way to make sure people like you, good hard working honest people, can get a fair deal from the insurance company so you can sleep at night without worrying you’re going to lose everything all over again.”
Mr Pierce interjected: "You know what James, I think you should be advising the Prime Minister"
“Well, he’s got my number. If he would like some advice, I’m more than happy to offer it to him, but I honestly think there will be implications at the ballot box in communities like Fishlake, in communities like Doncaster; there will be Northern communities right across this part of the country observing the Prime Minister’s reaction. They will see it as a proxy for how Mr Johnson might react when they could be the victims of a similar situation."