The battle between Anglo Irish Bank and Sean Quinn's family is likely to end up in the Four Courts in Dublin before the end of the week.
Sources confirmed reports that Mr Quinn's five children, who own the Quinn Group, may file suit against Anglo within days over the manner in which the group was seized.
The bank is also mulling legal action to compel Mr Quinn to disclose details of his assets and liabilities and may apply for a court order later in the week.
The moves come a fortnight after Anglo installed a receiver over the shares in the Quinn Group and seized control of the Quinn family's hotel and property interests.
The bank and joint-bidder Liberty Mutual are also taking over the Quinn family's insurance business.
Anglo had been hoping to secure the Quinns' co-operation in dealing with the family's €2.8bn (£2.46m) debt to the nationalised bank. But a meeting between Mr Quinn and Anglo bosses last week is believed to have ended without meaningful progress.
The Quinn children, who are believed to owe the bank more than €500m (£440m) stemming from their purchase of 15% of Anglo's shares, are to seek damages for their recent loss of the Quinn Group. The group was seized because it had been used as security when the children acquired their 2008 stake in Anglo.
Mr Quinn, who owes the bank more than €2bn (£1.8m), will not be party to that action, but has not ruled out taking a separate action of his own, it is understood.
The Quinns are considering an appeal to the sale of Quinn Insurance Limited (QIL) and have gotten legal opinion claiming the decision to put QIL into administration was not valid.
Meanwhile, Anglo is considering going to court for an order that would compel Mr Quinn and his children to reveal details of everything they own and everything they owe. The bank is keen to have a complete picture of the Quinns' wealth when it makes a decision on how to resolve the debt situation.
Sources stressed the legal actions could run for years.Mr Quinn’s five children may file suit against Anglo within days over the manner in which the group was seized