AIB has been accused of "filleting" files to remove information that does not support its arguments against two men who are alleged to have masterminded a €920m property loans fraud.
A London court heard accusations that the bank had removed specific paper documents from their files surrounding the case of Achilleas Kallakis and Alexander Williams, who both deny a raft of fraud charges.
George Carter-Stephenson, counsel for Mr Kallakis, told the jury that notes of meetings between AIB staff and his client had disappeared.
Mr Kallakis and his business partner deny 23 fraud and money-laundering charges relating to loans they took out from the bank between 2003 and 2008 to buy a series of high- end commercial properties.
They are said to have used falsified rental guarantees from a Hong Kong property company in order to secure the loans.
The defence has argued that all of the proceeds from the buildings went to a trust which was set up to benefit Mr Kallakis' children and to which he acted as a consultant.
Mr Carter-Stephenson, in court yesterday, said references to the trust had been removed from files by AIB and Mr Kallakis was listed as the principal in the deals.
He also referred to an AIB staff member who said he was too busy between 2003 and 2007 to take, and also transfer, notes to an electronic system.
"Is it these notes disappeared because they don't support what AIB say?" Mr Carter-Stephenson said.
He suggested that there was evidence to indicate the files had been "filleted" and references to the trust had been removed.
The comments came on the third day of closing arguments in the trial of the two men, which began in September.
They are accused of using falsified rental guarantees from Sun Hung Kai Properties, a reputable Hong Kong property giant which says it knows nothing of them.
Mr Carter-Stephenson questioned the role of former chairman Walter Kwok and deputy managing director Mike Wong who said previously that they had no knowledge of the two men.
He told the jury that if they could not decide on whether the guarantees were genuine or not, then the prosecution case falls.
The case will continue on Monday.