SDLP's Claire Hanna: I'd never become a Fianna Fáil MLA
Senior SDLP member Claire Hanna has said she would never be a Fianna Fáil MLA ahead of a conference on the parties' proposed partnership.
The SDLP membership meets on Saturday to discuss the planned link-up.
Ms Hanna criticised the proposal and said she supports an amendment that seeks to include other parties in the arrangement.
She told BBC's The View programme on Thursday night: "It is the exclusivity of it that I have a problem with."
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In January, Fianna Fáil and the SDLP announced a partnership arrangement but insisted they were not merging and would retain distinct identities.
SDLP members are to vote on the plans on Saturday at a special party conference in Newry.
"I believe strongly in the values of the SDLP and the new Ireland it embodies and I don't think putting all those eggs in the Fianna Fáil basket is consistent with that," she said.
'I can't become a different brand'
Ms Hanna, the party's Brexit spokesperson, added there was "no evidence" that the proposed partnership will work.
She said that while "of course something needs to be done" to halt the decline in the SDLP vote "we need to be very sure we have thought through all the consequences and we have explored all the possibilities, and I don't think we have".
"I have no problem working with Fianna Fáil but I don't see why we have to repudiate our links with Labour and Fine Gael," she said.
The South Belfast MLA was absent from an event to announce the partnership in Belfast in January.
She ruled out joining Fianna Fáil in the event of a merger.
"I don't see any scenario whereby I would be a Fianna Fáil MLA... I am not a kick the chairs and slam the doors type of person. I have been in the SDLP all my adult life.
"I am not a box of cereal, I can't suddenly become a different brand," added Ms Hanna.
A daughter of SDLP veteran Carmel Hanna, Ms Hanna has been a party member since the age of 16.
She became a councillor in 2011 and an MLA four years later.
Last November, two prominent Fianna Fáil members were sanctioned after unveiling a candidate for the party in Omagh, County Tyrone.