The Dáil has heard new claims surrounding the treatment of businessman Denis O'Brien by the former Anglo Irish Bank.

Speaking under Dáil privilege, Social Democrats TD Catherine Murphy says IBRC accepted a personal guarantee from the businessman to issue a loan to another man - despite having concerns about existing loans to both men.

Deputy Murphy claims Mr O'Brien gave a personal guarantee in order to secure a bridging loan for the property developer Paddy McKillen, when both owed large amounts to the bank.

She said the proposed was brought to IBRC by Richard Woodhouse, a bank executive who managed Denis O'Brien's accounts with the bank.

"So essentially, a man that owed huge debts to IBRC was granted a loan from IBRC, on the guarantee of another man who owed significant sums to IBRC - while there were questions over both men's financial ability to fulfil their original loan agreements to IBRC," she told the Dáil.

"Those making the decision were the ones directly connected to the SiteServ deal and other transactions."

The comments were made during a debate on legislation to grant extra legal powers to the Cregan Commission of Investigation into IBRC and its sale of SiteServ.

The inquiry is to investigate 38 transactions in which the bank wrote off debts of over €10 million, but its inquiry into the SiteServ transaction has been stymied by concerns about its ability to overcome the legal and client privilege enjoyed by the bank's clients.

"The point I'm making is: the larger transactions - those in excess of €10m, those in excess of €100m... some of htem may be more straightforward than some of the smaller transactions that give us some sort of a better understanding of the relationship that was taking place in the bank."