They make the bizarre claim in their first paragraph that given a post-Brexit recession, the government would not be able to deal with it. Reason apparently is that: "With interest rates near zero and debt still high, the Bank of England and Government would have limited ability to prevent such a recession."
Well, the existing near-zero rate may well preclude an interest rate cut. But that doesn't rule out fiscal stimulus. Ah, you might argue (as indeed the above 70 seem to suggest): but fiscal stimulus drives up the debt, and that's already too high. But fiscal stimulus doesn't have to be funded by debt: as Keynes pointed out in the 1930s, it can be funded by new money. Indeed, that's exactly what we've done over the last three years or so: that is, we've implemented traditional fiscal stimulus (government borrows money, spends it and gives bonds to those it has borrowed from), and followed that up with QE (central bank prints money and buys back the bonds). That all nets out to "the state prints money and spends it," as suggested by Keynes.
So... have the above 70 economists actually studied economics? Have they heard of Keynes? Have they heard of QE?