One of the strangest features of a dismal general election was the almost complete absence of the union from the political debate. Despite Scotland coming pretty close to voting for independence five years ago – and Northern Ireland’s well-documented civil strife – the future of the United Kingdom barely registered as a campaign issue (aside from Matt Hancock striking a pose, of course).

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If Boris Johnson thought the union was safe, the election results should have forced a rethink. With the Scottish National party vote surging, Nicola Sturgeon has already demanded a second vote on independence. Across the Sea of Moyle, more Irish nationalists than Ulster unionists were returned to Westminster for the first time since the creation of Northern Ireland almost a century ago. Inevitably, talk of a border poll on Irish unity has ratcheted up.

The union’s difficulties, as is so often the case, have mostly been caused by those who claim themselves to be its strongest defenders. The Tories’ full name is the Conservative and Unionist party – though it’s not always obvious.

“Get Brexit done” might be a winning line in England – and parts of Wales – but it has placed the union in a perilous position. Both Scotland and Northern Ireland voted decisively against leaving the European Union – there is little sign of that opposition mellowing.

In Northern Ireland, the DUP has paid a heavy price for supporting a Conservative government. And while some have written off the Scottish nationalist surge as purely an anti-Brexit wave, the scale of the SNP’s success attests to a rising sense of anger among independence supporters.

Facebook Twitter Pinterest ‘In Northern Ireland, the DUP has paid a heavy price for supporting a Conservative government.’ Alex Easton of the DUP loses out to the Alliance party in the North Down constituency. Photograph: Michael Cooper/PA

Johnson likes to depict himself as the UK’s staunch defender, but he has purged his party of the moderates who could make a genuine unionist pitch. And unlike his predecessor, Theresa May, Johnson appears to have little or no intrinsic affection for the union. However, that doesn’t mean he is about to give the green light to the referendums that would be needed for any constitutional change in Scotland or Northern Ireland. Quite the opposite.

Johnson has already said that he will not permit another independence referendum, but conventional wisdom has it that the prime minister’s intransigence will melt away over time, just like his opposition to a border in the Irish Sea – and that another SNP victory in the 2021 Scottish parliament elections will force a rethink.

Really? Johnson has shown his willingness to goad his opponents and run roughshod over long-held conventions. He could very easily keep saying “no” to Scotland – and gain support in England by being seen to stand up to the uppity nationalists.

The situation in Northern Ireland is, as ever, more fraught. The big election story is the success of the cross-community Alliance party, who doubled their vote and won a famous victory in North Down.

The increasing number of Northern Irish voters who refuse to break along sectarian lines will decide its constitutional future. Many come from what would be traditionally unionist backgrounds: these are middle-class Protestants who want to live in a modern, functioning UK but might at some point choose to live in a still-to-be-defined new Ireland rather than a backward Northern Irish statelet ruled by a fundamentalist, kleptocratic political class.

A vote on Irish unification could still be some time away. A border poll can only be called by the Northern Irish secretary, based on a reading of opinion polls. Once again, it is not hard to imagine a Johnson appointee refusing to heed the referendum calls that will likely grow after Brexit is done.

But belligerence is hardly a long-term strategy for the union. Sooner or later, the public will need to be asked if they want constitutional change. And that’s where things could get very messy.

As it currently stands, any referendum on the union in Scotland or Northern Ireland would be open to all manner of electoral manipulation. Dominic Cummings – whose Vote Leave campaign was found guilty of breaking electoral law in the 2016 referendum – has just masterminded a general election campaign, alongside Lynton Crosby’s protege Isaac Levido, that elevated lies and misinformation to party policy.

Having won a huge victory by playing the system, Johnson has no motivation to change Britain’s outdated and ineffective election laws. (In a grim irony, the Tories would doubtless have triumphed without industrial scale dissembling but having jacked open the Overton window there is little chance of them shutting it now.)

Imagine what a border poll on Irish unity would look like in the current era of dark money and disinformation. The scope for malfeasance is so vast that the Constitution Unit at University College London has set up a project to examine how any future referendum on Northern Ireland’s constitutional future would best be designed and conducted.

Similar concerns are at play in Scotland. The 2014 independence vote was, on the whole, an optimistic affair. There were endless town hall debates and public discussions. Another referendum would likely be very, very different.

The future of the union seems certain to be put to the test, sooner or later. After the general election we have just experienced, who would bet that it will be decided by a referendum that is genuinely free, fair and safe from foul play.

• Peter Geoghegan is investigations editor at openDemocracy. His book, Democracy For Sale: Dark Money and Dirty Politics, is published in 2020