The Taoiseach, Mr Ahern, has rejected a claim by the Society of St Vincent de Paul (SVP) that hundreds of thousands of children live in families whose income is less than €150 per week.
His remark was immediately disputed by the SVP, which insisted that its figures were fair.
The difference of opinion emerged after Mr Ahern opened the society's Christmas appeal for childrens' gifts at the Omni Park shopping centre in Santry, north Dublin.
After the formal opening of the appeal was briefly interrupted by about a dozen bin tax protesters, who were removed from the centre, Mr Ahern said that those contributing to the appeal at the shopping centre were "truly entering the spirit of Christmas".
Shoppers are invited to leave gifts at a collection point in the centre under a Christmas tree. Toys worth more than €70,000 were donated in a similar initiative last year.
While the Taoiseach said most Irish people were relatively well-off, he said there was still a need "for all of us to give a bit for those who need it most."
However, he disputed the SVP's suggestion that the families of 300,000 children lived on less than €175 per week. "There's not those kind of figures. The official figures of what people actually get in money terms do not show that."
The society defended the figures. Its local area president of Mr Pat Sheehy, said: "The figures would be accurate as specified."
He added that he had not heard Mr Ahern dispute the number.
Mr Sheehy said there had been a 94 per cent increase in "help calls" to the SVP this year. "We know that people are finding it very difficult. We know what the cost of living has been. We know how food prices have been going up. The basics will always hit the people on the margins more than any other group. They feel the pinch. The price of milk goes up, they feel it."
Mr Sheehy said he had thanked the Taoiseach for making himself available yesterday afternoon to switch on the lights at the tree.
"I think it is marvellous that he would come out here and switch on the lights because his presence here will attract so many people to come."
