LONDON — As Europe struggles to come to grips with its debt crisis, which has deepened with the collapse of Portugal’s government after it pushed for yet another round of budget cuts, three numbers stand out: 12.4, 9.8 and 7.8.

Those are the interest rates currently paid on 10-year government bonds for Greece, Ireland and Portugal. That they remain so high — compared with just 3.24 percent on German bonds — shows that investors remain unconvinced that Europe’s haphazard strategy for bailing out troubled, highly indebted countries has succeeded a year after it began.

As heads of state huddled in Brussels on Thursday, with a possible rescue of Portugal on their minds after similar bailouts of Greece and Ireland, the question remained: would Europe accept a resolution it has long resisted — forcing investors to take a loss on their bond holdings to keep the crisis from spreading?

While European stocks were stable on Thursday, credit markets remained uneasy, as the ratings agency Fitch downgraded Portuguese government debt and Moody’s de-rated 30 banks in Spain. If investors become more nervous about Spain — with a much bigger economy than Portugal’s, with higher levels of bank debt — the relative calm of the last couple of months could evaporate.