talian Treasury Minister Beniamino Andreatta called on Pope John Paul II yesterday to order the Vatican bank to assume responsibility for a debt of more than $1.2 billion that led to the collapse of Italy's largest private bank.

Andreatta said the problems that led to the failure of Banco Ambrosiano stemmed from its relationship with the Vatican Bank, which he said "has always denied every obligation of debt" with the failed bank. He called the Ambrosiano bank collapse "the largest postwar crisis in the world at the level of a single financial institution."

The Vatican Bank, which is known formally as the Institute for Religious Works, is headed by American Archbishop Paul C. Marcinkus, who reports only to the pope. It held 1.58 percent of Ambrosiano stock, making it one of the bank's largest shareholders.

"There is practically no way to confront the Vatican Bank because of the autonomy it enjoys . . . and its subjugation to the jurisdiction of the Vatican city-state," Andreatta said.

The controversy centers on letters of patronage exchanged between Marcinkus and Banco Ambrosiano president Roberto Calvi, who fled to London in June and committed suicide. Calvi used one of the letters to cover dollar loans amounting with interest to $1.287 billion to Panamanian dummy companies.

Andreatta has called on the Vatican Bank to make good on the loans, but they have refused, saying the letter of patronage was a "favor" that does not oblige them to honor the debt.

Marcinkus, of Cicero, Ill., has denied any wrongdoing.