There is one certainty as we survey our future: Britain must go through a highly complex and unprecedented procedure to detach itself from Brussels after more than four decades of European Union membership. The nation may have voted to leave, but there are many possible ways forward. So there must be torturous talks over several years with 27 states all seeking to protect their own interests, and the outcome felt in homes and firms across the country.

The negotiation results will shape our nation for decades. They could lead to the break-up of the union, disrupt sectors of the economy and alter Britain’s standing in the world. It is little surprise there are strong feelings on both sides of this debate over the best way forward given the hopes and fears. Yet suddenly there seems to be a sense of panic among those that pushed for this break as they close down discussion over the seismic consequences of the electorate’s decision.

The Brexit camp fought under the banner of democracy and sovereignty. Now they hurl insults at opponents

This is, of course, depressing – especially when the Brexit camp fought under the banner of democracy and sovereignty. Now they hurl insults at opponents who dare question their wisdom and howl down those who dare offer different perspectives on the way ahead. The ballot offered a binary choice without specifics. But ministers refuse to discuss Britain stance on departure deals, while politicians proposing that parliament should have a say are accused of subverting the will of the people.

I have sympathy for the prime minister, trapped by the electorate’s self-destructive verdict and swirling political realities. Clearly, divisions fuelled by the referendum are worsening, inflaming reluctance among leavers to accept challenge to their one-eyed view of the world after a shock victory. I saw this at the Tory party conference, where as someone opposing the idea of our nation turning inwards, I was constantly accused of being a sore loser. Typical was one leading leave voice who threatened to stop following me on social media since I refused to share his optimism.

Now Stewart Jackson, parliamentary private secretary to key Brexit minister David Davis, suggests “patriots” should stop buying The Economist due to its “Remoaner whining”. It is faintly sinister to see a de facto member of government claiming the sole mantle of patriotism for his views (while one might argue it is more unpatriotic to claim taxpayers’ money for your swimming pool, as he once did, than support a thriving UK-based global business). At the same time, a Tory councillor has launched a petition to make support of EU membership a treasonable offence.

These are inconsequential incidents involving minor figures, but they indicate a hardening intolerance of open discussion as the nation sets out towards its new destination. Look at how the BBC has come under attack, there is pressure on the Bank of England governor, and a firm that sought to put up prices on food became a political football. Knives are out for Philip Hammond, the chancellor, bizarrely accused of “arguing like an accountant seeing the risk of everything” for trying to protect the economy rather than pressing blithely ahead with Brexit. Bear in mind we are just at the start of the difficult process of extraction from the EU, with many bumps and potholes on the path ahead.

There can be just one reason those pushing Britain in this direction want to close down debate: a dawning realisation for them of the harsh reality of Brexit. Until now they have displayed breezy insouciance since their triumph, in some cases allied to foolish arrogance towards fellow Europeans with whom they must negotiate. Yet they have struggled to define a clear vision that stands up to analysis. Why else would they lack confidence to engage with their critics?

We have learned already the claim there would be a £350m-a-week boost for the NHS was simply a brazen lie. Now we see that Brexit means a plunging pound, rising food prices and potentially paying billions to Brussels to protect bankers. Leavers did not tell this to voters. Yet those who point out the difficulties of detaching a complex major economy from the octopus-like EU tentacles are condemned, just as they were previously charged with Project Fear by those people preaching a naive vision of spurious sovereignty.

No wonder they do not want too much debate, for here is the whiff of hypocrisy in the air. But then whereas Boris Johnson once wrote that “the plummeting of our currency” was “the definition of national humiliation”, now his Brexit fan club argues the pound’s plunge is good news, using Alice in Wonderland logic to explain away lack of international confidence in our future. At the same time, leading “liberal” leavers recoil in horror from a hideous immigration crackdown threatening firms to disclose foreign workers, yet this is the inevitable consequence of their ill-advised alliance with the crudest forces of populism.

So is this the democracy they promised voters: one in which people with differing views are accused of lacking patriotism? One where there are attempts to stifle debate? Priti Patel, one of the most ardent Brexit campaigners in the cabinet, compared negotiations with Europe to a hand of poker when she rejected a parliamentary vote on plans for withdrawal. We are not playing with a pack of cards, however, but with Britain’s future – and the stakes could not be higher for the entire country.