Dublin City Council has rejected the findings of a Government commissioned report, which concluded that the Poolbeg incinerator could incur more than €350m in penalties over its 25 year lifetime.
Extracts of the unpublished report were included in a letter from Green Party leader John Gormley to Environment Minister Éamon Ó Cuív.
A spokeswoman for the council said that was a 'hypothetical situation, which simply was not going to happen.'
The report said that the proposed incinerator could end up costing Dublin's four councils between €187m and €350m in penalties.
The report was completed last September by senior counsel, John Hennessy, who was contracted by the Department of the Environment to examine the financial viability of the plant.
Mr Hennessy concluded that the council's contractual obligation of delivering a specified amount of waste to the incinerator each year could prove to be 'extremely difficult' to achieve.
He said, if that happened, the contract allowed for 'significant penalties'.
Mr Hennessy estimated that even if EPA projections of growth in waste volumes happened, the potential total penalties could amount to €187.4m.
In a worst case scenario, the council could be obliged to pay the plant's operators, Covanta, €350.7m over 25 years.
In his letter, Mr Gormley says Mr Hennessy also found that the costs of abandoning or varying the project were much lower than claimed by Dublin City Council.
Dublin City Council spokeswoman Elizabeth Arnett said that while the report contended it would be 'extremely difficult' to secure waste - this was not the view of the Council, plant operators Covanta or the ESRI.
She said: 'It's a worse case scenario that simply isn't going to happen.'
She said a far more likely scenario was that the Councils would be paid €10m a year for the energy, which the plant will produce in the incineration of waste.
Ms Arnett pointed out that the plant had already passed An Bord Pleanála, the Environmental Protection Agency and the Commission for Energy Regulation.
The Irish Waste Management Association (IWMA) has called for the report to be released in full without any further delay.
'The Hennessy Report bears out many of our concerns, and highlights the huge financial risk that this project poses to taxpayers,' said Brendan Keane of the IWMA.
A Department of the Environment spokesman said the report was still being considered by both the Attorney General and the Government and would not be published.
