* Bento, former state debt agency head, worked at central bank
* Espirito Santo family's grip on bank seen diminishing (Adds quotes, details)
By Andrei Khalip
LISBON, July 5 (Reuters) - Banco Espirito Santo's main shareholder nominated an outsider on Saturday to lead the Portuguese bank after its previous choice faced opposition by regulators for being part of a team appointed by the bank's beleaguered founding family.
Espirito Santo Financial Group (ESFG), which holds 25.1 percent of BES, said in a statement it and other major shareholders would nominate Vitor Bento as the new chief executive of the country's largest listed bank by assets.
"ESFG is certain that by taking these decisions it has ensured BES's future development in this challenging environment," ESFG said in a statement.
It said it was seeking "a change in leadership which will help to strengthen shareholder confidence in BES". French bank Credit Agricole owns around 15 percent of BES.
Shareholders will vote on the nomination of the 60-year-old economist, formerly head of Portugal's debt agency and a department head at the Bank of Portugal, at a general meeting on July 31.
The meeting had initially been called to confirm Amilcar Morais Pires, the bank's chief financial officer, as the new chief executive, replacing Ricardo Espirito Santo Salgado, the founding family's patriarch who agreed to step down last month.
Sources familiar with the matter told Reuters that regulators were set to reject Morais Pires and sought a team of independent professionals to run the bank.
The Espirito Santo family has been under regulatory scrutiny since acknowledging in May there were "material irregularities" at a Luxembourg-registered holding company, ESI, through which it held part of its stake in the bank.
The family lost control of the bank in last month's 1 billion euro ($1.4 billion) capital increase.
The move to appoint Bento means its grip will likely diminish further after a clear signal from regulators that they want to isolate the bank from any fallout from the family's problems.
Local media have said Bento's appointment had the support of the Bank of Portugal, which has said that BES's solvency is solid and it is insulated from problems at the holding company.
"The Bank of Portugal has assumed a central role in managing the situation involving BES ... their influence in defining the new management is notable," said Filipe Garcia, head of Informacao de Mercados Financeiros consultants in Porto.
Earlier, sources said the Bank of Portugal had pushed for Salgado's resignation after the discovery of financial irregularities at the Luxembourg-based holding company.
ESFG also suggested Joao Moreira Rato be appointed as Bento's chief financial officer. He leads the country's debt agency IGCP and has been in charge of Portugal's successful return to debt markets after an international bailout in 2011.
Bento is currently chief executive of SIBS, Portugal's unified banking payments system that manages a vast network of ATMs. He also sits on the presidential advisory State Council.
BES shares have lost over 30 percent of their value in the past month, pressured, among other things, by uncertainty over the leadership change. But they rose 8.2 percent on Friday following initial media reports that Bento would be nominated.
Luis Goncalves, a trader at Gobulling brokers in Lisbon said the market hailed "the likelihood that this name could have the consensus of all main shareholders and would meet Bank of Portugal's wishes".
He said the new leadership "could start to separate the bank from the (Espirito Santo) group".
Under measures initially agreed with the central bank, which is responsible for vetting banks' leadership, the family would have had no representation on the new board, but ESFG wanted Salgado and family members to sit on a new strategic council.
Portugal's only banking dynasty, which began with a money-changing business in 1869, still controls many other assets via a complex array of holding companies, and family members sit on several Portuguese company boards, including Portugal Telecom.
$1 = 0.7331 Euros Reporting By Andrei Khalip; Additional reporting by Sergio Goncalves; Editing by Sophie Hares