Did Russia meddle in the outcome of the Brexit referendum, or didn’t it? It’s hard to think of a question more pertinent to this general election, and not just because some fear there may be dirty tricks this time too. Boris Johnson’s entire campaign strategy hinges on arguing that Brexit must be done, because it’s the will of the people.

The prime minister cannot admit any whisper of doubt about the legitimacy of the referendum, partly because leave voters would eat him alive for it, and partly because Brexit is his only really big idea. Without it, what is the great Conservative mission to change the country? All that would be left is a row about who should put right the damage his party did over nine years, and a promise not to be Jeremy Corbyn for those who find the idea of a Corbyn government terrifying. Without Brexit, the abyss beckons. And that’s the context in which Downing Street is declining to publish until after the election a parliamentary report expected to shed light on how we ended up with Brexit in the first place.

Since nobody can read the findings, it’s hard to know whether the intelligence and security committee’s conclusion is actually worrying or not, although the Tory-turned-independent MP Dominic Grieve has taken the unusual step as its chair of insisting voters need to see it. (The first rule of ISC, the only parliamentary committee cleared to operate within the intelligence services’ ring of confidence, is not to talk about ISC.)

As with other shady tactics, from Vote Leave’s illegal overspending to the lies that the outgoing EU president Jean-Claude Juncker this week accused Johnson and others of telling, it’s impossible to know if they actually changed the result: remainers are prone to underestimating how strongly many leavers felt, and my own suspicion is that claiming the vote was fixed may be easier than facing up to the real anger in some communities or the political failures that led here. But that’s the whole point of the ISC examining it.

Sitting on its findings until after the election has dangerous consequences for public trust in democracy. This is the first election I can remember where it’s possible to imagine people simply not accepting the result, especially if it’s close. No matter how disappointed we are in the outcome of an election, British voters generally grumble and get on with it. The unwritten rule is that losers accept they’ve lost, so long as winners promise to govern in everyone’s interest. But the smooth transition of power on which democracy depends is conditional on voters trusting that the process was fair. It is reckless beyond belief for governments to risk undermining that trust.

Election law badly needs overhauling. The Electoral Commission is struggling to follow the money, sometimes only identifying breaches of campaign funding rules long after the event. Tech companies are now worried enough about spreading misleading campaign material that Twitter has banned political advertising and Facebook is requiring greater transparency about who is behind it, although the latter still won’t fact-check ads.

Back in February, the Commons select committee on culture, media and sport released a landmark report on disinformation and fake news, arguing that electoral law “is no longer fit for purpose and needs to be changed”. Its chair, Damian Collins, is no conspiracy theorist but a Conservative alarmed by the evidence. We badly need an overhaul of the law to protect the integrity of our democratic process but instead what we’re getting is another snap election with no time for all that, a report withheld and an assumption that voters will just take all this in good faith. The prime minister should stop banking on a trust he has done nothing to earn.

• Gaby Hinsliff is a Guardian columnist