Greece, in its desperate struggle to avoid default, is unique. Europe’s policymakers defend this argument until they are blue in the face. But Portugal’s economic slump and grim battle to repay its debts are threatening to prove them wrong – and to place another storm cloud over the euro.

Portugal was not the central topic at the summit that European Union leaders held on Monday in Brussels. But it is a dossier they dare not leave untouched for long. If Europe is to banish the spectre of Greek-inspired contagion from its sovereign debt crisis, it may need to address Portugal’s plight within weeks rather than months.

As the leaders gathered in Brussels, the yield on 10-year Portuguese government bonds soared above 17 per cent, a record for the euro era. It is all but inconceivable that Portugal will regain access to debt markets in 2013, as foreseen under its €78bn EU-International Monetary Fund rescue agreed last May.