The businessman, whose legal case against stockbroker Davy six years ago brought about a Central Bank probe into the firm, has instigated further legal action against the company and a group of 16 of its former employees.
The courts website shows that an action by the developer and one of his Belfast based companies was lodged against Davy on Tuesday.
The case is also being taken against The O'Connell Partnership.
This was the name given to the consortium of 16 now former Davy employees who bought an Anglo Irish Bank bond from the businessman through the stockbroking firm in November 2014, without telling the man they were the ones buying it.
No other information is available at present to indicate what the reason for the new action is.
Last month, the Central Bank fined Davy €4.13m for regulatory breaches in relation to the 2014 transaction.
A number of senior figures in the stockbroker then left the firm and the company shut down its bond desk after the National Treasury Management Agency revoked its authorisation to act as a primary dealer of Irish Government debt.
Davy also subsequently appointed a firm of consultants to carry out an independent internal review, and it has been put up for sale.
In a statement regarding the new legal action, a spokesman for the stockbroker said: "Davy is committed to engaging constructively on all reasonable complaints and claims, however, as this matter was already the subject of a comprehensive full and final settlement agreement between the parties in 2016, Davy is obliged to defend this case."
"Davy cannot comment further as the matter is now the subject of on-going legal proceedings."