NCB has carried out a significant amount of brokerage work for the State, including some of the most lucrative privatisation contracts.
Founded by Mr Dermot Desmond in 1981, the brokerage grew to be the second-biggest in the State, winning a large chunk of State corporate business along the way. It was sold to Ulster Bank in 1994.
On several occasions, Mr Charles Haughey, when Taoiseach, denied he had influenced any of the decisions to grant Mr Desmond's company the contracts.
Last night, Mr Desmond angrily rejected any suggestion of impropriety, pointing out in a statement that during the period in question more than 100 similar contracts would have been awarded, and that NCB got no favourable treatment whatsoever.
Between 1987 and 1992, when Mr Haughey was Taoiseach, NCB and its affiliates were awarded nine contracts or consultancy arrangements from seven State or semi-state organisations, he said.
A competing stockbroker was awarded more than twice this number, he said.
"Only two of the contracts awarded to NCB required ministerial or Government approval," he added.
One of these was a contract awarded in 1989, when the company sold the State's stake in Tara Mines. NCB received £530,000.
The second was in 1991, when the State awarded the contracts for the privatisation of Irish Life to NCB. In the same year Irish Sugar - which became Greencore - appointed the broker as its adviser for the market flotation. Replying to Opposition claims, Mr Haughey insisted he had nothing to do with the awarding of the Irish Sugar business to NCB.