Wilkes, Jesús Aguado Soaring euro zone government borrowing costs are reviving fears of a replay of the debt crisis that 15 years ago rocked the bloc. Panic not, say analysts and investors: banks are better prepared.

Shaky public finances in the past created a so-called doom loop. Losses on holdings of government debt hit lenders, in some instances forcing state-backed bailouts and a further drain on budgets.

Funding costs will rise and market perceptions will matter, say analysts, as banks remain exposed to their countries' fiscal fortunes. But capital buffers and tighter supervision should help banks weather the turmoil, according to investors, analysts and data collated by Reuters.

"There is a limit to which you can insulate yourself from the domestic credit," said Simon Ainsworth, a senior banking analyst at Moody's Ratings. "Banks come from a better starting point but they are not immune." Since the 2010s crisis, the bloc has revamped banking supervision and armed the European Central Bank with tools to intervene, while banks have improved their defences, helped by years of record profits.

Yet sovereign concerns contributed to a 10% drop in European bank stocks (.SX7P) over the past six weeks — five times the wider market's fall (.STOXX) — a decline that follows a prolonged rally to 16-year highs. For France's top three lenders the fall has been 17% over the same period.

With its debt costs hitting 25-year highs amid a large deficit, social unrest and a 2027 presidential election where far-right and far-left candidates lead opinion polls, the euro zone's second-largest economy is in the eye of the storm.

Banks are allowed to treat government bonds as risk-free assets on their books. They count towards regulatory liquidity requirements and are used as collateral to borrow from central banks and other lenders.

Euro zone banks' net sovereign bond holdings have doubled since the crisis, reaching €4.3 trillion ($4.8 trillion) at the end of June, a Reuters analysis of European Banking Authority data showed.

However, banks' capital buffers have risen even more, lowering the ratio of sovereign holdings to capital lenders keep to cover potential losses below 2.5 from 2.7 in 2013. The lower the ratio the greater the banks' ability to sustain the hit from falling sovereign bond prices.

Both Axiom Alternative Investments Chief Investment Officer David Benamou and WisdomTree equity strategist Aneeka Gupta calculated that exposure to domestic debt for large French banks stands at roughly 15% to 30% of their best-quality capital.

That compares with more than 100% for banks in Italy in 2011-2012, the country at the forefront of the crisis then, Gupta said.

Still, falling government bond prices — which move inversely to yields — can saddle banks with losses if lenders need to align the book value of their bonds to market prices, or sell them to raise cash.

Proposals to strip government bonds of risk-free status or impose concentration limits have so far failed. But the EU Commission has included a further diversification of sovereign bond portfolios among steps needed to strengthen the banking sector, and will present its proposals in early 2027.

Even without formal rules, the ECB has prodded euro zone banks to reduce exposure to their home country's debt.

Domestic government bond holdings accounted for 41% of the total in mid-2026, the Reuters analysis of the EBA data showed, compared with more than 50% in 2013.

Also, banks have tripled to 60% the proportion of their bonds they value at cost — an accounting rule that enables lenders not to record losses when market prices fall.

By classing bonds as financial assets "held to maturity", banks can avoid booking capital-depleting losses on their holdings, unless they are forced to sell, a risk which Moody's Ainsworth said had shrunk because lenders rely less today on short-term funding.

Still, for Morningstar DBRS analyst Maria Rivas, the key question for banks is how investors view portfolios carrying unrealized losses regardless of the accounting considerations.

"If this is a temporary situation, it should not significantly affect investor sentiment. However, if it lasts over time, it could weigh on risk perception," she told Reuters.

Christos Megalou, CEO of Greek bank Piraeus (BOPr.AT), expects more volatility in government bonds but plays down the risk that it could snowball into a crisis.

Greece was now servicing its debts at average rates significantly below where Britain is borrowing today, he told Reuters, a sea change from a decade ago, when the country was recovering from a financial crisis and a string of bailouts.

France, now in the spotlight, is also in a different position that Greece was back then. "France is a very big economy and therefore has a lot of triggers to pull," Megalou said.

"The regulators, the policymakers, but also the banks, have battle-tested mechanisms to make sure that, most likely, we will not have a similar mega-problem again," he added. "Obviously we are doing stress tests in our portfolio all the time." Yet higher sovereign bond yields can hurt banks more directly by raising their funding costs because they come at a premium to government borrowing rates.

French banks are the largest wholesale debt issuers in the EU, so a permanently higher yield would raise their "cost of money every time they refinance, and that compounds", WisdomTree's Gupta said. A former senior banking supervisor, speaking on the condition of anonymity, agrees with that assessment.

Banks are competing more aggressively for deposits, a reflection of the funding pressures, and the outlook for the sector will ultimately depend, at least in part, on perceptions, the person said.