One of the hardest questions surrounding the British government’s approach to Brexit is how much of the blundering is down to incompetence and how much to duplicity. Duplicity suggests a plan towards which the lying is meant to contribute. It also requires a basic understanding of the facts: you cannot deliberately lie until you know what the truth is.

So where does the leaked Home Office document on Britain’s post-Brexit immigration policy that emerged last night fall on this spectrum? As legal experts were quick to point out on Twitter, the document not only contains errors; it also misrepresents the current EU arrangements around freedom of movement. “Highly misleading & inflammatory tabloid bullshit” in the words of one EU law professor, Steve Peers from the University of Essex.

Now ask yourself: why would you as a government put falsehoods in a proposal that is explicitly secret and for internal use only? Because you just cannot get your facts right? Or was the document meant to be leaked so this government could score a few points in the tabloids and the Daily Telegraph?

These are depressingly hard questions to answer with this government. When the international trade secretary and prominent Brexiteer Liam Fox announced in July this year that an EU-UK trade deal should be one of the “easiest in human history”, was Dr Fox being stupid or mendacious? Did the foreign minister, Boris Johnson, ever genuinely believe that Britain could “have its cake and eat it”? And what was David Davis on about when he claimed that the sequencing of negotiations in Brussels would be “the row of the summer”, only to roll over during the first meeting and agree with the EU demands – until revoking that agreement last month?

And, more pertinent to the leaked document, what was behind the promise made three months before the June 2016 referendum by the leading Brexiteer and MEP Daniel Hannan on Twitter: “It is irresponsible to scare EU nationals in the UK by hinting that their status might change after Brexit. No one’s suggesting such a thing.”

Did Hannan really think that after leaving the EU the rights of EU nationals would remain untouched? The rules for freedom of movement give EU nationals in another EU country more rights than the local population. This is an important reason why many Brits of Asian descent voted for Brexit – why should it be easier for a Pole living in Britain to bring over family members from Warsaw than for a British national doing the same thing with family members from Mumbai or Karachi?

Alas, whatever balance between stupidity and malice future historians will strike to explain this government’s Brexit policy, one thing should be abundantly clear for EU nationals living in Britain: they can no longer plan their future. The problem is not just that this government considers them bargaining chips for use in the negotiations (we’ll treat your EU nationals well if in return we can catch more fish): EU nationals have been aware of where they stand for over a year.

This government considers EU nationals to be bargaining chips for use in the negotiations

Suppose this government were now to disavow the leaked document and guarantee that nothing will change for EU nationals living in Britain? What would that promise be worth, from a government that has already performed one U-turn after another?

And even if this government did now stop lying, there is the question of competence. Earlier this year, 100 EU citizens living in Britain received a deportation letter by mistake – oopsie! Theresa May has stated that the European court of justice, which could protect EU nationals, will play no role in Britain post-Brexit. Or maybe this was a lie. Or perhaps a mistake because the prime minister had failed to grasp the role of the court?

If any EU nationals living in Britain were still in doubt, the leaked document should make it abundantly clear: for the rest of your time in Britain you will face genuine and fundamental legal uncertainty.

• Joris Luyendijk is a nonfiction author and former writer of the Guardian’s banking blog