The report in today's FT that an independent Scotland would likely not inherit the UK's AAA credit rating  will be seized on by opponents of secession as further evidence that, in their view, independence would be economically damaging. One unnamed agency told the paper that it could expect to receive an investment grade rating some notches below triple A. As the FT's Martin Wolf noted in a recent column :
A newly independent small country with sizeable fiscal deficits, high public debt and reliance on a declining resource for 12 per cent of its fiscal revenue, could not enjoy a triple A rating.
In an act reminiscent of his pre-election tactics, George Osborne has already warned, with little evidence, that the threat of independence is damaging investment  and that Scotland could be forced to join the euro (even without a formal opt-out, Sweden still hasn't joined after 17 years of membership).
Will Osborne now make play of the uncertainty over Scotland's credit rating? He may be wary of doing so, not least because there's an increasing chance that the UK could lose its own AAA rating. Others will rightly note that France and the US have seen little increase in their borrowing costs since their credit ratings were downgraded.
This hasn't stopped both Labour and the Conservatives going on the attack today. Scottish Labour leader Johann Lamont said it was "extraordinary that the SNP have not even approached the credit agencies for a draft opinion."
Scottish Conservative finance spokesman Gavin Brown said: "Ratings agencies are taken extremely seriously by investors all over the world and this warning is therefore deeply concerning: three of the top agencies agree that a separate Scotland would not be guaranteed a triple-A rating."
It's worth bearing in mind, however, that such scare tactics may only work to Salmond's advantage. Those who oppose Scottish independence need to remember that making the positive case for the Union, as Ed Miliband did in his recent speech , is as important.