THE SNP launches its manifesto today in an electoral situation more fluid than anybody can remember with just nine days left before we go to the polls. There is a chance the right words might make a real difference. The other parties have, after all, not come up with much.

The main challenger in Scotland, Ruth Davidson gave a car-crash interview to the BBC last week, which in its incompetence and incoherence outdid the earlier woeful performance of Theresa May under the keen questioning of Andrew Neil. I won’t go over once again the cruelty and stupidity of the two Tory women’s attitude to immigrants, but point to how it reveals some of the underlying postures that make them unfit to govern Scotland or the UK.

Davidson falsely claimed that Scotland had been unable to entice its due share of immigration because it had become a country “unattractive” to people from overseas, with taxes too high and growth too slow. As a matter of fact I do agree taxes are too high, and it does not help to see the Scottish Government seeking to push income tax higher still (while also wanting to lower other taxes – hence the impression of a shambles that I had enough to say about last week).

But this is a new situation, the result of extended powers for Holyrood that have barely come into effect as yet. It cannot possibly have affected the existing and previous levels of immigration to Scotland: the figures, from the Office of National Statistics (ONS), run two years in arrears, so that we are reading in 2017 about the situation in 2015. On this question Davidson is talking claptrap. In any event, in one way immigration has positively transformed Scotland’s economy by giving us a workforce younger and growing rather than older and shrinking.

As anybody would, I also accept Davidson’s contention that growth in the Scottish economy is too slow, though I draw diametrically opposite conclusions. Now the North Sea oil boom is over we see that almost none of the proceeds have been applied to solving our own underlying problems. The economy, if in a somewhat different shape, is just as sluggish as when the first drop of oil came onshore in 1969. The Scottish Government can be accused of having done too little to counter the effect of an inevitable end to the boom. But this to my mind is because the Scottish Government remains too timid and orthodox, tied even yet to a busted policy model which whenever tried over 50 years has proved to be a failure.

During those 50 years, as we often complained in Scotland, the oil money was used above all to paper over the steep decline in UK manufacturing capacity and the resulting deterioration in the visible balance of payments. We can see the result today in the comparative position of the UK and Germany: once they were roughly equal as manufacturing powers, but today Germany has 23 per cent of its economic activity in manufacturing while the UK has eight per cent.

The accompanying trade deficit shows that instead the UK imports most of the goods it needs. Economic decline has been spatially lopsided too: it has taken place mainly in the old industrial regions, the north of England, Wales, Northern Ireland and Scotland.

Expansion has been largely confined to London and the south-east of England, concentrated in financial services. Huge profits here let the UK as a whole keep up with its global rivals and remain one of the richest countries in the world. But it was done at the cost of creating in effect two nations internally, as the ONS analysis showed: three regions at one end of the island of Great Britain enjoy a surplus of net income while all the rest languish with a deficit. Does anybody in London have a clue what to do about this? Do they even ask the right questions? Unionist neglect and indifference are basic reasons for the lagging Scottish growth rate.

The reasons go back a long way. The regional policy of earlier times followed no coherent strategy. Either it tried to keep outdated companies going or else it sought to attract footloose investment – this at almost any cost, regardless of any particular project’s long-term viability. Foreign corporations arrived, collected subsidies from the UK Government for a few years and then departed, leaving empty the advance factories kindly provided for them and once again jobless the low-grade workers they had employed. Now that the public records of that era have been opened, we learn that the real motivation of the officials in the Scottish Office and the politicians they were advising lay in competition with other parts of Britain to win the biggest handouts from the Treasury. This was to them the measure of their success. The result today is the notional fiscal deficit which Unionists tell us makes Scottish independence impossible.

Devolution from 1999 did little to alter all this, and perhaps even made it easier for people in Westminster and Whitehall to forget about the Scottish economy. At any rate they have remained fixated on the south of England, and especially on sustaining consumer demand there after the great financial crisis of 2007. With traditional fiscal and monetary instruments useless, they have adopted a policy of creating asset bubbles, most obviously in housing, so as to make the homeowners of the suburbs and shires feel richer than they actually are. These efforts have usually failed, but nobody can think of anything else. Meanwhile average real wages have fallen by 10 per cent.

In Scotland we have seen little by way of bubbles, and were presumably meant to make do with the pickings from North Sea oil.

In 2017 those pickings are no longer to be had either, but again there is no better suggestion from Westminster and Whitehall. The one big change in our economic environment is the prospect of taking Scotland out of the EU against its will.

But the Scottish Government’s request to secure special arrangements to protect its economy has been ignored. In particular, we will be deprived, by stricter curbs on immigration, of the extra foreign workers we still need. England’s prejudices define Scotland’s interests.

This is the dismal background to the launch of the SNP’s manifesto. It has been trailed as a contribution to the formation of a progressive alliance at Westminster, and it will pitch into the current arguments about UK economic policy.

Even for Tories enormous deficits are the new normal, with repayment conveniently put off for the next generation of politicians some time in the third decade of the century. Whether at this moment it is right to make the deficits still more enormous is a moot point.

My fellow columnist George Kerevan yesterday put forward the idea of golden rules that would have current spending limited by the growth rate in the economy as a whole, while the level of capital spending would be judged by the prospect of return on it. I agree these are useful ideas for the control of the public sector in the UK of the present and the Scotland of the future.

But for the Scotland of the future these ideas still leave unanswered, indeed unasked, the question of how we are going to bolster our private sector, so that consumption is not just met by imports. Only from a stronger private sector in Scotland can our other desires be fulfilled. We have at the moment an inert and underperforming economy of subsidy and consumption, when what we need is a flourishing and entrepreneurial economy of investment and growth. The key test of the SNP’s manifesto is whether it will make any contribution to that prospect, or whether it can be binned along with the rest of the election literature.