Sean Quinn's family used the Quinn Group as their "personal bank" the High Court has been told.
Lawyers for the former Anglo Irish Bank told the court the Quinn children took €1.95 billion out of the group to fund their personal lifestyles, property acquisition, and losses from investments related to shares in Anglo.
Senior Counsel, Paul Gallagher, representing the Irish Bank Resolution Corporation, said €1 million was spent on Ciara Quinn's wedding at the then Quinn Group owned, Slieve Russell Hotel in 2007 and was never repaid.
Mr Gallagher said the money taken out was far in excess of what the Quinn children were entitled to and jeopardised the financial stability of the group.
Mr Gallagher was responding to claims made by lawyers for the five Quinn children in the opening of their case against IBRC and its liquidator, Kieran Wallace.
The Quinns claim guarantees and share pledges given by them in relation to loans of more than €2 billion are invalid and have no legal effect and they say they are not liable to repay €83 million each.
They claim they were unduly influenced by their father, who was in control of the Quinn Group businesses and they claim the bank behaved in a "morally reprehensible way" towards them.
They were not told of the perilous state the bank was in and were never advised by Anglo to take independent legal advice, they allege.
But Mr Gallagher told the court today the children's case was "extraordinary". He said there was an attempt to paint them as having no business experience, an inability to get independent advice and as living on modest salaries.
He said the case was "laden with cynicism" and it beggared belief that guarantees and documents related to the loans would have been signed without the children knowing what they were about.
The Quinn children claim the guarantees were required by Anglo for loans it gave to the Quinn companies to try to unwind their father's investments in the bank's shares.
Mr Quinn had invested hundreds of millions of euro in financial instruments called CFDs which allow someone to bet on the performance of shares. When Anglo's share price collapsed, he suffered huge losses.
The bank lent him money to fund the losses in order to prop up Anglo's share price.
Mr Gallagher said that although the children were claiming they had been acting under the influence of their father, they had not joined him as a party to the case.
He said the "highly intelligent" children, were the controlling shareholders in Quinn Republic of Ireland, the core group and had signed a shareholders' agreement under which they were to get a continuing and important role in the business of the company.
He told the court huge sums had been extracted from the core group for the children's benefit and in relation to the investments in Anglo and substantial property acquisitions.
He said the children had alleged that signature templates were used and their signatures were copied and pasted. But he said the bank was not involved in any such practices.
He said their suggestion that their father ran the companies, even though they had legal ownership of them, was not borne out by documents. He said they were involved in "so many aspects" of the transactions.
Mr Gallagher said the children had concentrated their attention and resources in a most "sophisticated and devious fraud" in taking assets from their international property group which should have gone towards repaying Anglo loans.
He said that activity had continued in very recent times, despite a host of injunctions.
Although the children were being presented as naive and unsophisticated, he said they had engaged in complex and sophisticated transactions and orchestrated a dismantling of assets from the IPB.
The case is expected to last around six months.