AXA boss: A Greek exit will not fix Europe

(CNN) -- Greece's elections this weekend could trigger the country's exit from the euro -- but even that might not save Europe from splintering, the head of insurance giant AXA has warned.

Henri de Castries told CNN "a Greek exit won't solve everything," adding the problems in Europe are "more complex than that."

De Castries, a fan of Greek mythology, believes a Greek exit would be akin to opening a Pandora's box. "Opening the box is very tempting before and very disastrous afterwards," he said.

De Castries said there were "flaws" in the construction of the euro which have created the cracks. "It was a case of putting the cart before the horse," he said. "Economic policies were not converging enough and the disciplines were not strong enough to allow for a stable position in the long run."

The worst-case scenario, according to de Castries, would be a disorderly default by Greece leading to its collapse out of the euro. Further, Italy and Spain could suffer bank runs that could exacerbate the bloc's pain.

However, such an outcome could be avoided should a moderate party win a majority in the Greek elections, securing the country's future in the eurozone, he said.

De Castries points to the Spanish banking crisis as one which must be resolved so Europe can allay concerns about the strength of its firewalls. "We need to be sure that we don't just have the fire brigade," he said, "but that water is coming out of the pipe. The Spanish case is a good test for that."

AXA, the second-biggest insurer in Europe, has been offloading its investments in Greek debt -- at a 78% write-down -- and no longer buys Italian and Spanish debt, as it seeks to distance itself from the deepening crisis.

De Castries said the company's investment portfolio is being kept diverse: "We have approximately 80% of our assets in bonds, of which half or a little less are in sovereign bonds. The other half is in corporate bonds and 20% are in other asset classes such as equities and real estate," he added.

CNN's Anna Stewart contributed to this article