“Brexit to cost £2,000 million a week, says government’s own report.”

That’s the claim plastered across a new pro-Remain campaign bus as it begins its 33-stop tour of the UK today.

It follows in the tyre tracks of another political wagon, which toured the streets of Britain in the run-up to the EU referendum in June 2016. But there, the similarity ends.

FactCheck tells the tale of two buses. Buckle up.

Background

Before the EU referendum, the Vote Leave campaign famously made the following claim: “We send the EU £350 million a week. Let’s fund our NHS instead.”

FactCheck and others quickly shot this down. The Eurosceptics were counting Britain’s gross contribution to the EU budget, but ignoring the fact that we got a substantial amount of the upfront fee back in the form of a rebate, as well as other smaller sums.

The head of the UK Statistics Authority said Vote Leave’s continued use of the £350 million was “misleading and undermines trust in official statistics.”

What’s the new bus all about?

Now a group called Brexit: is it worth it? have jumped on the bus bandwagon. The design of the bus echoes the Vote Leave campaign bus which generated publicity for Boris Johnson and the others.

The group describes itself as a “grassroots campaign to tell the truth about the costs of leaving the EU.”

The campaign was initiated by a group of people based in North London who “support Britain’s continued membership of the European Union”. This group is affiliated with the Britain For Europe organisation, which believes “continued UK membership of the EU is necessary.”

The bus campaign has been crowdfunded by “ordinary people from around the UK”, raising a total of £16,253 from 661 supporters. That works out at quite a large average donation of just under £25 per person.

We can’t verify the identity of donors with complete certainty, but a couple of the names sound familiar. They appear to include a high-profile member of the House of Lords, a famous historian and a bestselling writer, among others.

The campaigners say it is “focused on voters who supported leave in the referendum but are now having second thoughts or beginning to change their minds about Brexit.” They are travelling across the UK, taking in places like Dover, Glasgow and Birmingham.

The original crowdfunding page says the bus “will certainly stop outside Parliament, the BBC and the London homes of some of the extreme Brexiteers in the Cabinet.”

Why do they think Brexit will cost £2,000 million a week?

The bus makes it clear that the campaigners are relying on Government figures to back up their claim.

They told FactCheck they are getting the numbers from a leaked government report, some of which has been reported in the media, which tried to predict what would happen to the UK economy in a number of different Brexit scenarios.

A spokesperson for the campaign explained how they reached that number:

UK GDP is currently worth about £2 trillion.

Without Brexit, we could have expected GDP to reach £2.7 trillion by 2032 – a 35 per cent increase.

If Brexit goes ahead, we leave the single market and strike a trade deal, we can expect GDP to rise by just 30 per cent by 2032. That means GDP would be worth £2.6 trillion in today’s prices.

So that’s a difference of £100 billion a year from 2032, or around £2 billion a week (they write it as £2,000 million instead of £2 billion on the bus).

Is this misleading too?

There are a few issues here, which we think you might miss if the bus drove past you in the street.

The £2 billion a week figure is not directly comparable to the £350 million figure claimed by Vote Leave. That number – spurious though it was – represented actual money being spent by the UK taxpayer. Today’s figure is about the size of the economy. It doesn’t equate to money that a government would be able to spend on the NHS or anything else.

To be clear – we are not talking about the economy shrinking as a result of Brexit. We are comparing two scenarios in which GDP continues to go up. It’s just that we can expect it to grow more slowly if we leave the single market.

From what has been leaked so far from the government report, there is no mention of this £2 billion a week figure. The campaigners have had to do quite a few back-of-envelope calculations to arrive at this number, and it’s not clear that the government economists who did the original work would endorse it.

It’s also not clear what the government’s own analysis was assuming as part of the Brexit scenarios. For example, did they expect a deal on free movement of people? Or special arrangements for the UK financial services sector? There are so many variables here that even the government can’t fully anticipate – any one of which could shift the total cost of leaving the EU.

The £2 billion a week figure is not a cost we are paying now: it’s an estimate of how big a potential shortfall might be in 15 years’ time.

There are estimates of how much Brexit has already cost us – but they are much lower than this long-term figure. Mark Carney, the governor of the Bank of England, has said that the UK has forfeited £200 million a week in lost revenue in the two years since the Brexit vote.

Despite those caveats, it’s worth saying that before the referendum, the Treasury and several other independent economists published similar predictions, all based on the idea that leaving the EU would damage growth. The leaked government report revises the numbers slightly, but still concludes that in every Brexit scenario, growth will suffer in every region of the UK.

Of course, there is ultimately no way of FactChecking predictions like this, but we know that the government are not alone in making these forecasts.