Figures reveal a special lower rate of tax available to property developers cost the Exchequer €800m.
The tax rate was introduced to free up land for development in 2000 and was scrapped in January 2009.
When land is sold for development purposes it is liable for income tax, but not capital gains tax.
Figures from the Revenue Commissioners show the tax was used in 10,000 cases between 2000 and 2007.
Accountancy experts estimate the cost to the Exchequer was €800m over that period.
The so-called 'Special Incentive Tax Rate' was introduced to encourage the release of land for residential development.
The special incentive rate was 20%, as opposed to the higher rate of tax of 42% which was later reduced to 41%.
The incentive meant that money from the sale of land was not liable to the health levy or PRSI.
The amount of revenue forgone by the Exchequer is significant considering urban and rural renewal tax incentives, which attracted considerable criticism, cost the taxman €2bn.
Former Taoiseach Bertie Ahern has said when tax incentives for developers were brought in, ‘the place was disastrous’ and now he said he is very proud to look at the quays in Dublin.
However, he said that ‘like everything something runs its course and then it was time to do away with them and that's what Minister Cowen, then as Minister for Finance, did.’
Mr Ahern also ruled himself out of the running as Dublin's first directly-elected mayor, unless such a role would have ‘full executive powers’.
He also said he has no problem giving evidence in public to the banking inquiry, if he is called to do so.
Mr Ahern said, however, he had no idea if he would be called as a witness.
