Mr Johnson hits the election campaign trail in Scotland this morning to unveil more than £200 million of funding for farmers north of the Border.
But he arrives after Sir John launched a broadside during a speech in Glasgow last night on the hardline approach of Mr Johnson’s new administration over the past week, which has seen a purge of Tory grandees such as former chancellor Kenneth Clark and Sir Nicholas Soames over their opposition to a no-deal Brexit.
The former Tory leader warned Brexit would strengthen the prospect of Scottish independence, as Nicola Sturgeon told MSPs at Holyrood yesterday she planned to place independence at the centre of a coming election campaign.
Sir John slammed the Government’s attacks on opponents of Brexit as he addressed business leaders in Glasgow.
He warned: “Ahead lie many challenges.
“If we are to meet them, we need Government of the highest quality, not Government by bluster and threat in a climate of aggressive bullying.
“Without decisions in the long-term British interest, we will fail future generations.
“We need our four nations to come together as, perhaps, they have never done before.
“And yet, at this very moment, when unity is so crucial, our United Kingdom is being torn apart by the divisions of Brexit.”
In a veiled reference to Mr Johnson’s controversial strategy chief Dominic Cummings, he slammed the role of “over-mighty advisers”. He added: “Get rid of those advisers before they poison the political atmosphere beyond repair.”
MPs expelled from the party should be reinstated, according to Sir John, or the Tories will be seen a “mean-minded sect”.
“The Government must change its tone,” he said.
The new regime has “no majority and no mandate”, Sir John went on, with the Cabinet branded a “faction of a faction with no counter-balance to hold it back”.
The prospect of Scottish independence is “growing”, but the ex-PM warned this will “weaken every part of the United Kingdom, including Scotland.
“Even legitimate resentment is no basis for wise and thoughtful policy,” he said.
“The fiscal gap, higher taxes, lower spending. The vulnerability of greater isolation. They will affect every Scot.”
He added: “If we let nationalism divide us – Scottish nationalism and English nationalism – we will create a schism that cannot be bridged.”
Mr Johnson visits the north-east of Scotland this morning to unveil a £211.4m boost for Scottish farmers. An extra £51.4m over the next two years will complement the £160m allocated in the spending round announced on Wednesday.
Mr Johnson said: “For too long, Scottish farmers have been given a poor deal by the EU’s Common Agricultural Policy, which is why we are taking this opportunity to change things for the better.
“I made a pledge to resolve the historic funding gap for Scottish farmers and delivering on this promise has been a priority since I became Prime Minister.
“Today’s announcement was the first step in making sure future funding is fairly allocated across the UK, taking into account the unique farming environments in Scotland.
“Once we are out of the EU, we will have a historic opportunity to introduce new schemes to support farmers – and we will make sure that Scottish farmers get a fairer deal.”