In a world as complex as ours, slogans are more important than they have any right to be.

When questions of how to organise society, distribute resources and conduct relations with our neighbours fox even the greatest of experts, it’s human nature to run for the shelter of an easy explanation.

The shorthands we use to skip over messy realities – “budget responsibility”, “war on terror”, “migrant crisis” – shape our understanding of them, for good or ill. They are what linguist Geoffrey Leech once described as “concept forming”. That means that, in any contentious debate, getting in there early with a pithy phrase is half the battle.

It’s a clever formulation, and appears to sum​​ up the possibilities of the post-Brexit era.

When it comes to Brexit, the most intricate political problem Britain has faced for decades, it’s clear who’s been winning the war. “Take back control” was a stroke of genius, boiling down the problem of how to improve lives in an interdependent world to a simple question of self-determination. “No deal is better than a bad deal” was good too: despite the fact that leaving the EU without any kind of agreement represents the worst outcome of all, it recast the government’s weakness as defiance. And now we have the “Brexit dividend”, the fiscal bounty that leaving the world’s largest trading bloc will apparently deliver.

It’s a phrase you’ll have read a lot in the past day or two. As “allies of the foreign secretary” briefed that he was to demand an extra £5bn for the NHS in cabinet this week, it kept cropping up – sometimes with and sometimes without inverted commas, depending on the level of scepticism applied. Johnson “will not relent on demands for a £100m a week Brexit dividend until it is secured”, wrote the Times. His Brexit brother-in-arms Liam Fox backed him up. “I think it’s very useful to remind people that we will get a dividend from leaving the EU,” he told the BBC.

Maybe they were taking their cue from Jacob Rees-Mogg, who told the Sun on Sunday: “Brexit is a great opportunity for the UK to build a new independent trade policy that delivers jobs, cheaper food and clothing — an immediate Brexit dividend for the British people.”

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Perhaps they’re ultimately inspired by “peace dividend”, a phrase first used in 1969 to describe the money that would no longer have to be spent on the Vietnam war if it were brought to an end, and used much more widely at the end of the cold war. In any case, it’s a clever formulation: it’s neat, catchy, and appears to sum up the possibilities of the post-Brexit era. The contribution the UK currently makes to the EU budget will soon be ours to spend however we see fit.

But it’s a blatant lie. There is no “Brexit dividend”, because the net effect of Brexit is to cost the UK money. As the FT set out in excruciating detail before Christmas, leaving the EU doesn’t come cheap. Forget the “Brexit divorce settlement”, the forty-odd billion that covers existing budget commitments and some other costs such as pensions. We haven’t even left yet, but the uncertainty has already zapped 1.3% of GDP, according to estimates – the equivalent of £340m per week. And before you counter that this is still less than the fabled £350m a week that was plastered on campaign buses during the referendum, remember that that figure, too, was a lie. The rough cost per week of EU membership adds up to more like £136m – some of which funds regulatory agencies we benefit from and will have to replicate after we leave.

So the phrase “Brexit dividend” should definitely come with flashing lights and sirens, and at the very least inverted commas. But I fear it’s too late. The concept already has currency, and may be unstoppable. It’s incumbent on those who see it for what it is to point this out at every opportunity, and perhaps come up with a reality-based version. Reality, in this case, may be too depressing, too unglamorous a rival. But at least “Brexit burden” or “Brexit penalty” have the ring of truth.