The environmental engineer who blew the whistle on the methane gas emitted by the Irish Glass Bottle (IGB) site in the Dublin docklands said it remains a mystery why investors paid out €412m for the heavily polluted site that was used as a dump for Dublin waste.

Malcom Doak, who formerly worked as an inspector at the Environmental Protection Agency, said that the current cut-price €60m valuation put on the IGB site by the Dublin Docklands Development Authority (DDDA) takes no account of the huge cost of monitoring and capping continuing emissions at the site.

A number of Davy Stockbrokers staff are on the list of over 40 investors who invested €62.5m to fund Bernard McNamara's share of the development at the site. McNamara, who last week admitted that he was broke and owes banks €1.5bn, owns the site with the DDDA and Derek Quinlan.

It also emerged last week that Davy clients had separately lost €120m investing in Barry O’Callaghan’s education publishing empire in the US.

Davy is owned by 50 to 100 of its staff who bought it from Bank of Ireland for €300m at the height of the boom.

It is understood that its leading shareholders, including Brian McKiernan, David Smith and Tony Garry, hold between 4% and 9% of the company.

But sources close to Davy said its reputation had not been damaged by the losses and that the big high-profile cases were unwinding. Sources said Davy recognised the losses for its clients by writing down the value of their investments at an early stage.

The broker continues to make money and paid staff annual bonuses in recent weeks and has no problems in meeting its debt repayments to Anglo, market sources said.

Many senior investment experts in Dublin predict that the next big wave of disputes to reach the courts will be from small one-off developers or investors, whose loans for under €5m will not transfer into Nama.