It's no secret that there's little love lost between Turkey's policy makers and ratings firms.

Turkish cabinet ministers and central-bank officials have long bemoaned raters' stance on Europe's fastest-growing economy, stressing that Turkey's credit rating – which all three big firms rank below investment grade – is too low. Ankara has repeatedly fulminated against Fitch, Moody's and Standard & Poor's, hurling accusations of an anti-Turkish bias in their sovereign-ratings analysis. After Fitch lowered Turkey's outlook in November,...