Three Fianna Fáil Senators have issued a statement criticising the Government's Civil Partnership legislation.
Senators John Hanafin, Labhrás Ó Murchú and Jim Walsh said the Bill, as currently drafted, is flawed in a number of ways.
The legislation, which passed all stages in the Dáil last week, is due to be debated in the Seanad tomorrow.
Its passage into law is not in doubt as it has the support of the Opposition parties, but sanctions for the Fianna Fáil senators could follow if they do not support the Bill.
In their statement, the three senators said the legislation weakens the special status of the family and marriage.
The senators will be tabling thier own amendments to the Bill.
It is not clear whether they will vote against, in favour, or abstain in the division.