SF's fiscal plans are not mathematically possible

On RTE Radio 1, Mr Adams suggested among other things that the best paid workers would enjoy a low tax rate of 7% on salaries over €100,000.

But he also suggested that the highest earners would be facing a marginal tax rate of 59 cent in the euro.

He explained the discrepancy by saying that it would depend “on how much they spend”.

This is not the first time that Sinn Fein has got into difficulties on economic and financial matters. Last year the party’s South Down Westminster candidate Chris Hazard got into difficulties on the Nolan Show when he suggested that government should clear people’s credit card debts, car loans and mortgages.

But it is logical that a party as shamelessly populist will end up in such hoops.

The republican party is right to support lower corporation tax in Northern Ireland (to match the Republic) but lowering the tax burden of wealthy companies hardly sits easily with its socialist rhetoric.

Sinn Fein is of the school of thought that raising tax is a painless thing that can be paid for by some villainous unseen other: the wealthy. But it espouses spending schemes so extravagant that the entire wealth of the top 1% could be confiscated and it still would not come close to footing the bill.

And in any event, it has hardly seemed to be in a rush to crack down on border fuel criminals – the sort of tax cheats who, by evading their responsibilities, mean that the rest of us have to pay even higher rates of fuel duty to make up the lost income.

Sinn Fein might be the most shamelessly incoherent on tax policy, but all the main Stormont parties adopt a low tax, high spend policy.

Such a policy is only sustainable in Northern Ireland if someone else pays the shortfall, which of course someone currently does: mainland British taxpayers.

You don’t hear Sinn Fein advertising that truth.