Independent MEP Ms Dana Rosemary Scallan has said she is against the Government's abortion referendum proposal.
Ms Scallan, speaking after a vote in the European Parliament on funding for embryo research, said that the wording of the Government's proposals and their implications for embryo research meant she could not support the referendum.
She wants protection, under Irish law, for embryos which have not been implanted in the womb. The vote in the European Parliament, she said, would leave Ireland "an open door for unethical and unconstitutional research using child embryos".
"I will certainly not vote for it [the referendum], that's for sure, and as much as I can I'll make clear my position," she said on RT╔ radio.
The controversy centres on the use of embryos which had been produced in the in vitro fertilisation procedure but not placed in the womb and which would otherwise be destroyed.
However, Fine Gael MEP Ms Avril Doyle, who is also a member of the committee, said the vote "quite specifically" meant that only research legal within each member-state would be allowed and the embryos used would be those which would otherwise be destroyed.
"This has nothing at all to do with the abortion referendum," Ms Doyle said.