The Government has been asked to clarify that a further €8 million will be cut from its Overseas Development Aid budget (ODA).
The Trócaire chairman, Bishop John Kirby, said Ireland must fulfill its international obligations in reaching the UN target on overseas aid by 2007 and expressed his disappointment at news of the further cuts.
It was learned in June that €32 million was being taken off the aid budget as part of a round of Government cutbacks.
Bishop Kirby said the budget estimates, due in November, will "be the test of the Government's mettle and its commitment to the poor".
The Taoiseach Mr Ahern is due to address the UN Earth Summit in Johannesburg tomorrow and Bishop Kirby said it was a chance for the Government to allay any fears about its commitment to the poor.
He said any statement by the Taoiseach about Ireland's commitment to reaching the UN target by 2007 would ring hollow unless there was an obvious rise in the percentage basis year-by-year.
Referring to Mr Ahern's announcement two years ago that Ireland's ODA would reach 0.7 per cent by 2007, the Trócaire chairman said: "It seems we are going backwards and the opposite has happened. This year our aid allocation fell to 0.41 per cent. It should be 0.45 per cent".