YOUR columnist is cowering in my journalist’s dugout, sheltering from a political bombardment directed at me by Finance Secretary Derek Mackay and my old mate Andrew Wilson, author of the SNP Growth Commission Report. Derek (in Saturday’s National) and Andrew (on Good Morning Scotland yesterday) were scathing about my proposed amendment to the SNP leadership’s big economic motion to Spring Conference.

I want the first post-independence parliament mandated to establish a separate Scottish currency. They, though supportive of such a currency, eschew setting a specific date for its introduction. Who is right and does it actually matter either way?

Let’s back up a moment and celebrate a major, strategic change to the SNP’s currency stance. During the 2014 referendum campaign, the SNP wanted to keep the pound sterling as Scotland’s post-indy currency. More specifically, the SNP wanted Scotland to stay in an agreed currency union with rUK, much as New Zealand and other former colonies had done previously, as a way of facilitating mutual trade.

The political small minds in the Better Together camp rejected the proposal outright and even hinted rUK would do everything it could to thwart a common currency. The issue became the Achilles’ heel of the independence case.

Fast forward to 2016 and the setting up of the Growth Commission, with a remit to rethink SNP economic policy. When it was finally published last year, Andrew recommended a shift to establishing a separate Scottish currency. But there were big caveats. Sterling would stay for an indefinite period until economic conditions matured to allow the switch. Specifically, Andrew argued that the notional public-sector deficit inherited on independence would have to be eliminated first, and economic growth doubled to the European norm for small industrial nations of circa 3%.

Internally, the Growth Commission thought that process could take a decade, perhaps longer. Which would leave the Bank of England in charge pro-tem of deciding Scotland’s interest rates. This “vassal state” idea did not go down well with the SNP’s membership when the Growth Commission was debated at a series of internal National Assemblies chaired by Keith Brown. Members had tried selling sterling on the doorstep in 2014 and it hadn’t worked. They were dubious about a variation that promised voters a new currency sometime, “just not yet”. If anything, that calculated ambiguity is an even worse line to sell.

Just as problematic, the Growth Commission also proposed a “fiscal rule” for an independent Scotland, whereby the first percentage point of annual economic growth would be devoted to paying down any inherited public deficit.

At the current Scottish average growth of 1.5%, that would leave a meagre half point to sustain cash-hungry public services. This opens the SNP to (exaggerated) Labour charges of austerity. True, achieving higher growth would eliminate this problem. But how do you get higher growth if independent Scotland has conceded control of interest rates to the Bank of England by keeping sterling? And if you can get higher growth without a new currency, why bother?

Disquiet in the membership has caused a big rethink at SNP HQ. This month’s Spring Conference will now debate a blunderbuss, four-page motion supporting the Growth Commission findings, proposed by Derek Mackay and Keith Brown. Let’s leave aside their calculation in putting such a ridiculously long motion to conference: it’s practically unamendable without descending into chaos. More interesting is the obvious change of emphasis in the motion regarding currency.

The official line now is that introducing a new Scottish currency will be a key component of the indyref2 message, not a vague optional extra sometime down the road, which is where the Growth Commission parked it. The conference motion mandates an incoming SNP government to “complete” preparations for starting the new currency during the first, post-independence parliament. To that extent, the membership has prevailed.

However, serious ambiguities remain. For starters, the latest proposal is to have Holyrood vote annually on when to push the button for a new currency, based on six “tests” proposed in the original Growth Commission report. An annual vote actually creates economic uncertainty for businesses. If you believe in waiting till “the timing is right”, as Derek argued in Saturday’s National, then do so. But an annual cliff-edge, “will-they-won’t-they” debate will lead firms and lenders to freeze vital decisions on investment, till they get clarity. Which is why I favour a definite timetable to introduce the new currency. Derek and Andrew remain unconvinced and are determined to block any commitment to a specific timetable. They offer a host of platitudes to explain why: “Rome isn’t built in a day”, and “currency serves the economy, not the other way about”. But their real worry is that potential Yes voters are nervous about a currency change.

A Survation poll last month did find that 40% of voters were “less likely” to back independence if Scotland had its own currency. Of course, those particular voters are most probably in the No camp anyway. More surprising, fully 42% said they were “neither more nor less likely to support independence” as a result of a currency change, suggesting (post-Brexit mayhem) that voters are no longer moved by Project Fear arguments. Instead, they want clarity and leadership on economic policy.

This brings us back to the Growth Commission proposal for a “hard” fiscal rule; ie diverting the first percentage point of annual economic growth to paying down any potential public deficit inherited on independence. Strangely, this is the one major Growth Commission recommendation missing from Derek and Keith’s portmanteau motion to conference.

I suspect dropping the fiscal rule is meant to assuage membership opposition and deflect Labour criticism. But there is a timebomb here. The nebulous six tests suggested by the Growth Commission boil down to eliminating any inherited deficit before introducing the new currency – City lenders to the Scottish Government will insist on it. So the fiscal rule can’t be ducked. It’s the first thing Andrew Neil will ask about in any indyref2 television debates. To trigger the currency, under the procedure proposed by Derek and Andrew, you first have to eliminate the deficit. That implies cuts or at least much slower spending increases. And the less you spend, the less you grow.

But if you introduce the new currency in the first parliament, the problem goes away. For starters, borrowing in Scottish currency from Scottish savers reduces undue financial pressure from the City of London. Second, issuing Scottish denominated public debt creates a local asset for savers. Translated: there is less pressure to reduce the Scottish deficit arbitrarily. The elected Scottish government can borrow, invest and grow the economy as it determines.

The bottom line is this: you either introduce a Scottish currency on a timetable, or you cut the deficit on a timetable. It’s one timetable or the other. Derek Mackay’s motion to Spring Conference implies a “deficit first” strategy which I find unacceptable. I hope the SNP membership does too.