A High Court judge in Belfast has said a controversial deal by Anglo Irish Bank appears to be "improper and unlawful".
Mr Justice Deeny was referring to the "Golden Circle" transaction where the bank loaned 10 of its clients 451m euros which they then used to buy shares in the bank.
The transaction was a share-support scheme, designed to prevent a large number of shares being sold on the open market which would have depressed the bank's value.
Anglo lent the money on a non-recourse basis, meaning that if the borrowers could not repay the bank, would simply take back the shares.
The judge made his remarks in the course of judgement concerning a dispute between Anglo and a firm controlled by Belfast businessman Peter Curistan.
Mr Curistan's firm, Marcus Ward Ltd, has been granted an injunction to prevent the bank winding up the company over an alleged £10m debt.
Marcus Ward leases two units in the Odyssey Pavillion in east Belfast.
Another of Mr Curistan's firms, Sheridan Millenium Ltd (SML), had a long lease on the whole of the Pavilion.
The case focused on Anglo's behaviour when attempts were being made to sell the Pavillion lease in 2009.
At that time SML owed Anglo around £80m and the lease was worth around £43m.
SML needed to find a buyer who would take on the Anglo debt.
It was Mr Curistan's case that the bank effectively acted as an agent in the sale process and thus owed his companies a duty of care.
The bank has admitted that it did introduce potential buyers from its customer base.
On this basis the judge concluded that there is "at least an arguable case" that the bank was under a duty of care.
The bank's preferred bidder was the Belfast firm PBN.
It is owned by Paddy Kearney and Neil Adair. Mr Adair is the former manager of Anglo's operation in Northern Ireland.
There was another bidder, referred to only as "Confidential Five".
The judge said this firm showed "persistent interest" in the deal even after they were initially told they were unsuccessful.
At one point "Confidential Five" was even offering slightly more than PBN.
"Confidential Five" was also offering that £15m of the Anglo loan would be on a recourse basis whereas the PBN bid was entirely non-recourse.
In effect that meant if PBN took over the Pavillion lease and the business failed Anglo would only take back the lease rather than pursuing the company for any of the loan.
Encouraged by the bank, Mr Curistan opted for the PBN bid. However, in November 2009 the bank decided not to go ahead with the PBN deal.
There is a dispute between the parties about why the bank took this course of action.
However, the judge referred to an internal Anglo email from December 2009.
In that email it was stated that the bank did not want to make a non-recourse loan to PBN and Paddy Kearney because it had become public that Mr Kearney was part of the "Golden Circle".
The judge refers to the Golden Circle transaction as "a prima facie improper and unlawful proceeding".
The judge agreed that there was "a clearly arguable case" that the exposure of the Golden Circle was the real reason for the deal falling through.
Mr Curistan's lawyer argued that Anglo had been in breach of a duty of care by not disclosing that Mr Kearney was "party to this improper arrangement."
He added that it was arguable that if Mr Curistan had known about Mr Kearney's part in the Golden Circle they would have taken the offer from "Confidential Five."
The judge granted Mr Curistan's company an injunction preventing a winding-up order on the basis that there is "a genuine and substantial dispute."
Those matters of dispute are now likely to be the subject of further legal proceedings.