During the EU referendum campaign, the Vote Leave campaign repeatedly reassured the British people that a vote for Brexit would boost the economy and create jobs. And they dismissed all expert warnings of the consequences of a vote to leave - from the Bank of England, IMF, Treasury and others.
But Monday has seen just the latest in a series of shockingly bad economic numbers. It's less than six weeks since Britain voted to leave, but already the consequences are being felt. The Markit PMI survey of manufacturers, which picks up data every month on output, orders, employment and other metrics, has collapsed into negative territory. Falling from 52.4 to 48.1, it is now at its lowest level for four years.
What does this rather dry statistic really mean? It means lower revenue for firms as orders dry up. It means small businesses being forced into the red. It means jobs being lost and investment postponed or cancelled in a desperate attempt to save money. It means real people, workers and business-owners alike, being worse off.
And it's hardly the only piece of evidence that the Leave vote has drastically hit the economy. The pound has plunged to its lowest level since the mid 1980s, before many voters were even alive. Confidence among both consumers and retailers is now lower than it's been since the height of the Great Recession in 2009. And big companies like Ford and Ryanair are mulling their investment positions in Britain.
I campaigned passionately for Britain to remain in the EU, and was deeply disappointed by the result. Yet I respect it totally, and I hope now that Britain can avoid economic damage, and get the best deal possible from the EU. We Remain campaigners take absolutely no pleasure in being the bearers of bad news.
Yet it's vital that the Leave campaigners are held to account for the promises and claims they made during the referendum campaign. Senior cabinet ministers, from Boris Johnson and Andrea Leadsom to David Davis and Priti Patel, promised greater prosperity outside of Europe, and blithely brushed off every warning about the consequences. These people aren't running some scrappy political campaign - they're running the country. They have to be held to account, and that is what Vote Leave Watch, the campaign I chair, is doing.
There is a tragic irony that it is manufacturing that seems so clearly to be bearing the brunt of the Brexit vote. Theresa May entered Downing Street promising a "comprehensive industrial strategy", which would shift the economy towards productive manufacturing, and rebalance the country by boosting manufacturing heartlands in the North, the Midlands, Wales and Scotland. I applaud the intention, though we are yet to see much in the way of specifics.
The irony is that the part of the economy the new Prime Minister wants to champion is the very sector that has apparently been badly hit by the vote for Brexit. While she earnestly reassures the nation about her commitment to an industrial strategy, her government is packed full with Leave campaigners who have made that strategy immensely more difficult to carry out.
Chuka Umunna is the Labour MP for Streatham and Chair of Vote Leave Watch