Banco Espirito Santo SA saw its bonds slide after its biggest shareholder, Espirito Santo Financial Group SA, sought protection from creditors, the third such request in a week from companies affiliated with the bank’s founding family.

Central bank governor Carlos Costa has tried to reassure depositors and investors that Portugal’s second-biggest bank by market value can withstand any losses after some of Grupo Espirito Santo’s units missed commercial paper payments. He said last week he wants to avoid tapping a fund set aside for recapitalizing banks under the country’s $105 billion bailout fund.