If the start of 2012 began with a significant skirmish and a tactical advance for David Cameron, as he initially took control over the independence referendum debate, the start of 2013 has been less successful for the pro-UK camp.

In fact, it seems to have suffered minor wounds from friendly fire. On Saturday, the Herald splashed a story that the Treasury had estimated that - based on the Scottish government's own data - the average Scot would be £1 a year worse off under independence.

That boiled-down line wasn't quite what Danny Alexander, the Lib Dem chief secretary to the Treasury, had hoped for. Instead, he handed his opponents a quick and easy riposte: pay a pound for freedom.

As the piece reported, he was aiming at the Scottish government's and Yes Scotland's assertions that Scots would be £500 better off under independence – a figure based on one exceptionally good year for North Sea oil receipts.

The briefing to the Herald – something of a quiet holiday season story to keep the pot simmering – was intended to show that over the full 12 years of devolution, the Scottish government's own figures showed the Scottish economy suffered a marginal pound per head annual deficit. The paper quoted Alexander saying:

Basing a case for Scotland to be independent forever on one good year of oil revenues is incredibly misleading and very foolish.

That argument (the Government Expenditure and Revenues Scotland figures studied by the Treasury show a 3.8% deficit between Scottish spending and taxes, including oil revenues) might excite economists, but it won't many others.

And given the notable and unexpected absence of any major New Year offensives by either side on the referendum debate, this story was gleefully seized on by Yes Scotland, who span it in its favour.

Blair Jenkins, the pro-independence campaign's, quickly launched his "pay a pound for Scotland appeal".

Equally quickly forgetting that Yes Scotland has recently distributed one million leaflets promoting a similar line that every Scottish family would be £1000-better-off under independence, Jenkins stated:

If the cost of creating a more equal and fairer Scotland was only a pound, I believe most Scots would think that a price worth paying.

He focused instead on the last five years (ignoring the lean ones and selecting the fat ones) by insisting Scotland was easily able to afford independence, but he then played the Treasury's own hand against it: if even the independence movement's foes could only find a modest economic downside, what then, Jenkins asked, was the problem?

It is remarkable that at this early stage in the campaign, the Treasury has conceded that people in Scotland would be financially no worse off under independence. Of course, the truth is that Scotland is already better off and will continue to be so after independence.

While fluffing his lines (referring to the pro-UK Better Together umbrella group as the "yes" campaign), Cameron dutifully came in to back up Alexander's line during yesterday's coalition relaunch:

I think there are important arguments of both the head and the heart that need to be made in this great debate about the future of our United Kingdom, and [I think] when it comes to the arguments of the head, things like would Scotland be better off, I think we will be able to show, categorically, that Scotland would be worse off, would be less well off.

While precision, accuracy and credibility on the economy are absolutely crucial to both sides, the political impact of this spat will be shortlived and minor: it's all a bit of knockabout, which the Yes campaign has had the wit to find the humour in. They know it won't be a campaign theme worth pushing too hard.

After all, many nationalists will remember Salmond's ill-fated "penny for Scotland" campaign during the first Holyrood election in 1999 (a reference to new powers to alter income tax rates in Scotland after devolution) which rather failed to play-up the ambitions he wanted then to champion.

But equally, few voters will remember that far back or find it relevant. So it all leaves Treasury and Scotland Office officials wincing somewhat at the way this gambit played out. Understandably reluctant to push it any further, they would rather wait to fire their bigger guns – in the form of far more detailed, new Treasury analyses due later this year.

Rather than replicate Cameron's New Year's offensive of last January, Salmond and his deputy Nicola Sturgeon are also calmly waiting, and they are likely to chose a quite different battleground while watching the UK government endure its own crises over welfare and taxation policies. With 2014, the referendum year, fast approaching and a 20 point deficit in support for independence to overcome, the next few months will prove critical to both.