The National Millennium Committee has insisted that a tree will be available for each household in the State despite Green Party claims that only 5 per cent of the trees will survive to maturity.
"The bottom line is that arrangements have been built into the scheme to ensure that there will be a tree corresponding to each household," said a spokesman.
"Trees which die will be replaced. The project has been welcomed by 98 per cent of environmental and conservation groups."
This follows criticism of the project from Dublin North Green Party TD Mr Trevor Sargent and Friends of the Irish Environment.
While welcoming the move to improve native woodland cover, Mr Sargent said that only an estimated 35,000 of the 1.2 million trees planted would reach maturity.
"Unless 25 million broadleaf trees are planted and dedicated to this project, then the National Millennium Committee's message that each household will have a tree for generations to come will be exposed to ridicule."
A spokesman for Friends of the Irish Environment said the tree certificates issued to households were "a scam forced on the Millennium People's Forest project by the National Millennium Committee for political spin".
Material released under the Freedom of Information Act by the Department of the Taoiseach showed that the project as proposed by Coillte had no element of individual certificates for every household, the spokesman added. The project was planned for the State as a whole.
The spokesman said the committee, and the Government Chief Whip, Mr Seamus Brennan, had insisted on the issuing of certificates as a condition for an additional £1 million in funding.
"The scientific fact is that of the 1.2 million trees planted, only 5 per cent will survive to maturity because of the thinning necessary in growing broadleaves.
"In order for the 1.2 million certificates to represent mature trees, more than 25 million would have to be planted. Instead of the proposed core woodland planting of 337 hectares, 6,000 hectares would be required."
However, Mr John McLoughlin, project manager, said all trees in the 14 forests which did not survive the first five years would be replaced with healthy saplings.
"After 35-40 years, the majority of trees planted will still be present. After that, under the natural selection process, the stronger trees will suppress the weaker trees, as is natural. "After 60 years, the forests will be semi-mature, and, will, naturally, regenerate themselves by producing millions of seedlings on the forest floor."
Mr McLoughlin said it was impossible to estimate how long an individual household tree would survive. A household whose tree died could be assigned another tree, which would be a new tree planted in another location in the designated forest, or one naturally regenerated from fallen acorns and seed.
