I have been around long enough to know that I should not always be surprised or shocked about what is written in the Sun newspaper. But it was reported yesterday that Boris Johnson was telling cabinet colleagues he was “basically a Brexity Hezza” – with the newspaper helpfully explaining this was a “reference to Tory wet Michael Heseltine who battled rightwing PM Margaret Thatcher”.

The quotes have not been denied and I assume they were well sourced. Part of me is even a little flattered, not least because there is a side to the prime minister that I like. He succeeded me as MP for Henley and I got to know him. More importantly, as mayor of London, he once showed a capacity to govern in the tradition of one-nation conservatism.

Let’s be clear that one nation is about governing for the whole country – rich and poor, young and old, black and white, north and south – in a way that unites rather than divides

There is, however, a “but” – a very big “but”. Because a “Brexity Hezza” is a simple contradiction in terms. My commitment to Britain being part of Europe and maintaining our influence in the world goes to the heart of my politics. And I fear that any traces of liberal conservatism that still exist within the prime minister have long since been captured by the rightwing, foreigner-bashing, inward-looking view of the world that has come to characterise his fellow Brexiters inside the Downing Street bunker. It is simply not possible to be a “one nation” Conservative and also pursue a “Little Englander” strategy obviously crafted to appeal to the likes of Nigel Farage and his followers.

The belated publication of the government’s Yellowhammer plan shows ministers are preparing for soaring food and fuel prices, shortages to medicine supplies and public disorder on our streets. They have no democratic mandate for no deal because they explicitly ruled it out in the last referendum. And they are not doing this in response to some natural disaster or act of war: they are doing so because of a policy they are voluntarily ready to impose on the British people.

Instead, this would be an act of grotesque self-harm inflicted on the people, the economy and the public services of our country by our government.

There is a danger that terms like “one nation” lose all meaning if they can be attached to any policy, especially one like this. So, for the avoidance of any misunderstanding, let’s be clear that one nation is about governing for the whole country – rich and poor, young and old, black and white, north and south – in a way that unites rather than divides.

A one-nation leader does not respond to the resurgence of the far right by pandering to their narrow, nationalistic, xenophobic and, yes, racist agenda on immigration. Or react to a rise in knife crime by making headline-grabbing announcements about more police, when it is not the lack of police that caused the problem so much as a failure to rebuild inner-city communities and improve failing schools. He or she wouldn’t risk the investment on which our vital manufacturing industries depends or be reckless with the fragile union between the four nations that make up our United Kingdom.

Perhaps most importantly, such a leader would not consider whether he and his government should obey the rule of law as an interesting topic for public debate – while silencing debate in parliament.

There is another aspect to the way this government behaves that I have found deeply troubling this week. Downing Street’s refusal to publish correspondence on when and how it decided to suspend parliament has been justified on the grounds that it would be unfair on ministerial advisers.

I do not believe this prime minister is pursuing the national interest. But it may be, if the opinion polls continue to tighten and the prospect looms of him breaking George Canning’s record as the shortest-serving occupant of Downing Street, that he realises his self-interest is best served by changing course.

Ultimately, the only way to solve the Brexit crisis he has helped create is to put this bitterly vexed question back to the people. A one-nation leader would let the whole nation decide.

• Michael Heseltine is a former Conservative deputy prime minister