When the ubiquitous Green party leader Zack Polanski was on the BBC’s Sunday with Laura Kuenssberg show singing the praises of wealth taxes last month, he said something that got my spider-sense tingling:

‘This isn’t about creating public investment, we can do that anyway, we don’t need to tax the wealthy to do that.’

On the face of it, this is a slightly odd thing to say. Other lefties, such as Richard Burgon MP, have argued that a wealth tax could be used to give more money to Our Precious NHS or remove the two child benefit cap. Polanski is right to say that we can have more ‘public investment’ without a wealth tax – we can tax other things – but why he is so eager to divorce tax revenue from public spending? He must know that voters are more likely to support tax rises if the revenue is earmarked for nice things, so why not flag up all the lovely public spending that the money could be used for?

The appeal of MMT to the ‘anti-bedtime left’ is even simpler. They want more money spent on public services but they don’t want to pay for it

My suspicion was that Polanski had fallen down the rabbit hole of Modern Monetary Theory (MMT). One of the hallmarks of an MMT disciple is the strange belief that taxes do not pay for public spending. Other red flags include an eagerness to point out that the government’s finances are not like a household budget and that money owed by the government to the Bank of England is money ‘we owe to ourselves’. It is not that these claims are untrue. It is just that nobody else feels the need the say them all the time. And that is because nobody else thinks they mean what MMT advocates think they mean.

Polanski was on the same show again at the weekend and this time he left me in no doubt. After making the case for a large increase in public borrowing, it was pointed out that we are at the upper limits of what the bond markets are prepared to tolerate and that we already owe £3 trillion. Polanski’s reply was telling. He said that loans from the........

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