Judge Martin Nolan at the Circuit Criminal Court also found another former executive of the now-liquidated bank, Pat Whelan, not guilty of seven charges that he was privy to the fraudulent alteration of loan facility letters.

FitzPatrick was found not guilty of charges of having provided loans to the wife and five children of bankrupt businessman Sean Quinn to enable them to buy shares in the bank, boosting its stock price.

FitzPatrick, who was previously chief executive of the bank until 2005, still faces a further 10 counts of providing unlawful assistance to investors known as the "Maple Ten".

Whelan and a third former executive, Willie McAteer, are also charged with illegally lending money to both the Quinn family and the Maple Ten.

The three accused have pleaded not guilty to all charges.

Acquitting FitzPatrick on six counts of providing illegal loans to the Quinn family to buy shares in Anglo in July 2008, judge Nolan said: "I've directed not guilty verdicts in relation to six counts involving the Quinn family." He did not give further reasoning.

In February, prosecutors said that Anglo, which was put into accelerated liquidation last year and whose failure cost some 30 billion euros ($41 billion), decided to do something "absolutely illegal" by lending money to the individuals.

Senior lawyer for the prosecution Paul O'Higgins told the jury on Wednesday that the remaining charges were not about whether or not the financial regulator approved, permitted or was comfortable with the lending, or whether other people said to have been involved in this transaction should have been prosecuted, but if the accused authorised or permitted it.

"In the case of Mr. McAteer and Mr. Whelan, they were directly instrumental, not just in authorising it (the lending) but in carrying it out themselves or through other people," O'Higgins said in his closing remarks.

"The prosecution will say in Mr. FitzPatrick's case, he did nothing, knowing about the lending and what it was for, or caused any step to be taken which might prevent it."

The three former bankers were put on trial in January in the first such case since a banking crisis, which cost taxpayers over 60 billion euros or about two-fifths of national output and forced Dublin to take an emergency financial aid package in 2010 from the European Union and International Monetary Fund.

(Writing by Sam Cage and Padraic Halpin; Editing by Catherine Evans and Susan Fenton)

By Sarah O'Connor