Sinn Féin has given its strongest indication yet that the controversy could damage its relationship with the DUP in the power-sharing executive.
North Antrim MLA Daithi McKay went further than his party's previous comments to suggest that republicans might even look again at their role in the newly reconstituted government.
If wrongdoing was proved, "we will review our situation within government", he told the BBC yesterday (Friday).
His generally released statement was more moderate but continued to put pressure on the DUP.
"Sinn Féin have deep concerns over the handling of the decisions about the visitors' centre at the Giant's Causeway by both the environment minister Arlene Foster and the Deti minister Nigel Dodds," he said.
Both are DUP ministers.
Declan O'Loan (SDLP, North Antrim) called for "absolute transparency" and for Mrs Foster to provide details of "all aspects of the private planning application for a visitors' centre including the recommendations given to her by the Planning Service regarding either approval or refusal of the scheme".
DUP junior minister Ian Paisley jnr, whose links to the developer first sparked questions, yesterday re-iterated that there had been no wrongdoing.
In reference to an interview on the Stephen Nolan radio show during which he said he "knew of" Mr Sweeney, he said: "Did I support this application? Did I know this man? I answered I think 'Yes, I know of him, yes.' I think that was exactly how I answered the question.
"It wasn't as if I was hiding anything. The answer was positive and in the affirmative.
"And that's I think where it ought to have been – but again I caution this should not be a discussion about the applicant, the colour of his skin, his religion or his politics.
"This should be a discussion about the quality of the application and what will happen."
