How much longer can Boris Johnson ignore the Brexit-shaped elephant in the room?

By the end of the decade, workers in the UK will be £470 a year poorer as a result of Brexit, according to analysts at the Resolution Foundation think tank.

For many people, this might be dismissed as the latest instalment of “project fear”. After all, it is just another forecast, a model, a prediction that will one day be proved wrong.

But it is one based on a growing amount of hard data built up since the 2016 referendum and, latterly, our exit from the EU 18 months ago.

It means we can start to separate what we know about Brexit’s impact from what economists expect.

We know that the pound fell sharply after the vote and it has not recovered to previous levels. We know that this makes it more expensive to import things. We also know that leaving the EU’s single market has exacerbated shortages of labour, though Brexit is far from the only cause. Additional paperwork, administration and box-ticking has increased costs for businesses trading with EU member states.

Most concerningly, investment growth ground to a halt in 2016 and it has not restarted again. Investment was increasing at 1.7 per cent per year before the vote and has averaged 0.1 per cent since. That may not sound like a huge amount but it is likely to make a big cumulative difference to the UK’s future prosperity.

Less money pouring into companies, factories, offices and laboratories, means a continuation of this country’s chronic problem of underinvestment and low productivity. Our ability to efficiently produce things will be less than it otherwise would have been. The northeast of England – one of Britain's poorest regions – is expected to be the hardest hit.

The high-wage, high-skilled economy that Boris Johnson has promised requires investment which has so far failed to materialise. This is, quite clearly, a problem caused by Brexit and it is one that looks set to continue for years. As is so often repeated, businesses crave certainty and if there is one thing that the government’s version of Brexit has delivered it is perpetual uncertainty.

Recent wranglings over the Northern Ireland protocol demonstrate that we are a long way from “getting Brexit done” and that Boris Johnson has shown a willingness to be at constant war with the EU. Portraying Brussels as the source of Britain’s problems has served his career well and can continue to do so. A hit to Britain’s long-term economic prosperity is of far less immediate political concern.

By 2030, when the accuracy of the Resolution Foundation’s forecasts can be fully assessed, the current prime minister will have long left Downing Street. Even if they are proved accurate, Johnson will not be there to be held accountable.

To avoid further damage to UK households’ incomes, what is required is a strong case to be made for a sensible relationship with our closest neighbour and largest trading partner; a case that speaks to people who voted to leave and one that cannot be cynically portrayed as undermining the referendum.

Sir Keir Starmer’s Labour Party has so far declined to put that case forward, fearing that it would risk losing some of its traditional voters for good. It is possible that it will become easier to make the argument, if the data continues to demonstrate the damage that Brexit has caused.

But, at present, the vacuum is being filled by politicians who appear willing to put personal advancement over the prosperity of the people they serve. The evidence is increasingly showing that we will collectively be poorer for it.