It first appeared during the independence referendum, when SNP politicians tried to dismiss concerns about the currency or their wildly over-optimistic predictions about oil revenues.
The Brexiteers seized it, and proponents of remaining in the EU were faced with the same charge sheet in 2016.
Well, after last week, nobody can be in any doubt that project fear was actually “project fact”. The extraordinary impact of a no deal Brexit has been laid out in stark terms.
Long border delays and increased costs to use your credit card on holiday were just some of the headline warnings, but even events like the Grand National face upheaval.
An extra six weeks of medicines are being stockpiled, and Brexit Secretary Dominic Raab couldn’t give an assurance that patients would not be affected by Brexit.
He joked to reporters that people will still be able to get a BLT sandwich. Great, but as one of my diabetic staff members in Edinburgh asked, what about insulin?
We already know that Brexit is going to hit Edinburgh hard. One study put the Capital sixth on a list of UK cities which stand to struggle the most when we leave the EU, due to the size of our highly-skilled service sector.
There is no such thing as a good Brexit: if we leave, jobs will be lost and livelihoods will be at risk. But it will be so much worse if we leave without a deal.
Last week, Mr Raab didn’t go into detail about what might happen to the financial markets in such a scenario.
While this will primarily impact on London, we are home to the UK’s second largest financial services sector, so there will be huge knock-on consequences.
Pantheon Macroeconomics has now warned of a likely drop in the pound by ten per cent, and the Bank of England would need to inject a staggering £100 billion into the troubled economy.
As well as impacting on our finance sector here in Edinburgh, there are also huge concerns about what Brexit will mean for our universities, particularly the cutting-edge research we perform here.
In a city that voted overwhelmingly to remain part of the UK in 2014, there are fresh warnings about what Brexit could mean for our constitutional future.
The ex-president of the European Council, Herman Van Rompuy, said at the weekend that leaving the EU without a deal poses an “existential threat” to the UK. The SNP government will, of course, be delighted if Brexit leads to an increase in support for independence – regardless of the cost to jobs.
So it beggars belief that the Scottish Conservative and Unionist Party is so willing to put the Union at risk.
Ruth Davidson was elected in Edinburgh Central because of her strong, public opposition to Scottish independence. Yet now she is willing to stand by and let Theresa May press ahead with a destructive Brexit which could jeopardise the UK’s very future.
If we have a no deal Brexit, the voters in Edinburgh Central – many of whom rely on the EU for their work – will remember that come the 2021 Holyrood election.
My Labour colleague Ian Murray has written to Ms Davidson, urging her to back a People’s Vote on the final Brexit deal.
She campaigned for Remain in 2016; she warned of the dangers of Brexit which are now becoming a reality – why won’t she join those of us who believe the public has a right to decide if this is what we really want for Scotland and the UK?
If we do not get the opportunity to vote on the deal, I fear catastrophic consequences for Edinburgh. That’s why I will remain fearless in my opposition to Brexit.