One of the most important jobs of government is getting the balance right between tax and spend. It’s a critical lever that impacts not just how much money people have in their pockets but the level of services government can provide, and indeed the performance of the whole economy.

Adam Smith’s principles of effective taxation have stood the test of time: equity, certainty, convenience and efficiency.

So not only should the tax system be equitable, or proportionate, with those who can afford to pay the most doing so, it should also promote certainty and transparency, with minimal chopping and changing of direction at short notice.

The principle of equity is generally agreed, but unfortunately not always followed through in practice. Certainty is often ignored, clashing as it can with the whims of political processes.

While taxes, like death, are viewed as inevitable the reality is that for the most part citizens are not uncomfortable paying tax - even higher taxes than their neighbours - provided they have comfort that the money is spent well on services they value. That social contract is important. Free education and prescriptions. Free or cheaper travel. Good local public services.

The cost of poor public services can be significant, far outweighing an additional penny or two on a tax bill, be that having to pay to go private because the NHS is failing to deliver its statutory waiting time guarantees, or making use of private education as a consequence of a lack of faith in state schools.

On the other hand tax rises, with nothing to show for it by way of service improvements, risks breaking that social contract.

The debate on tax is often reduced to a simple "tax and spend" narrative. Of course there is some relationship between tax rates and the quality of public services, but it’s far from the whole picture.

Read more: Focus on what really matters and Scotland can emulate Ireland

How public money is spent is critical. It is a truism to state that there is no limit to how inefficient a complex organisation or system can be. With more than 100 agencies and other quangos in existence across the Scottish public sector landscape – a number that rises inexorably despite best efforts to keep it under control – and a core Scottish Government civil service that now costs the best part of £800 million each year, largely to generate policy advice - there is always more that can be done to maximise the impact of public spending.

That could involve digitisation of services, removal of duplication and complexity across quangos, breaking down suboptimising silos, focusing on cheaper prevention rather than managing expensive symptoms or rationalising the vast public sector estate – running into tens of thousands of properties across Scotland. It’s more than 10 years since the Christie Commission mapped out more efficient and effective ways of delivering public services, something no-one would claim we have come close to achieving.

And there is of course a difference between tax rates and tax take. People will move to Scotland, despite higher taxes, provided that social contract is sound. The data shows that is the case. Attracting more well-paid workers, and raising wages (and hence tax take) through upskilling our existing workforce has the potential to generate far more revenue than any changes to tax rates.

Smith’s principle of equity is well accepted, but "progressive taxation" needs to be more than a sound bite to get through an election campaign, it needs to have substance and be able to stand the test of choppy waters – not abandoned when the going gets tough. The Marxist approach to principles (Groucho not Karl that is) doesn’t sit well with Smith’s requirement for certainty. Localism is important, and a deal is a deal.

Abrupt changes of policy direction just feed the narrative that things are not under control. The cost of living crisis - and its impact on policy making - isn’t something that just happened last week.

Progressive taxation needs to be about more than virtue-signalling, it’s a serious economic policy that stands on its own merits. Putting more money into the hands of those with the least ensures more of it finds its way into local economies. A focus on tackling low pay is also a key plank of this programme.

Delivering efficient, high-quality public services, supported by growing the tax base, is a critical part of the social contract. Sticking to principles delivers stability, creates confidence and builds support.

And when a tax is clearly regressive - putting a disproportionate burden on those least able to pay - it isn’t progressive to entrench it.

Ivan McKee is an MSP and former Minister for Business, Trade, Tourism and Enterprise