Coleraine Borough Council has voted unanimously to keep the proposed visitor's centre at the Giant's Causeway in public hands.
The issue of a visitors' centre is controversial
The DUP Mayor Maurice Bradley seconded a motion put forward by SDLP councillor John Dallat.
Several DUP councillors were among those who voted in favour of the motion.
Environment Minister Arlene Foster said she had been "minded" to accept a plan by private developer Seymour Sweeney.
On Tuesday, Sinn Fein called for the DUP to clarify its relationship with the millionaire developer.
Mr Sweeney has said he is a member of the DUP and had signed nomination papers for a party councillor but never gave "a penny piece" to the party.
It has also emerged that Ian Paisley Jnr bought a house in Bushmills at full market value from Mr Sweeney.
Seymour Sweeney said he had not given the DUP money
Ms Foster said it was "rubbish" to suggest that she was influenced by Mr Sweeney's membership of the DUP.
"I do not know the applicant, have never met him, and know nothing about him.
"If anyone impugns my integrity in this matter I will be seeking legal advice and will act accordingly," she said
The managing director of Seaport Ltd said he had never met Ms Foster or Nigel Dodds, the economy minister who has dropped plans to spend £21m of public money on the centre.
He said he has met DUP leader Ian Paisley who is the MP in his area of North Antrim and Ian Paisley jnr who is an MLA for the area.
North Antrim Sinn Fein MLA Daithi McKay had called on the DUP to clarify their relationship with the developer.
Earlier, chairman of the Causeway Coast and Glen Heritage Trust Dr David Irwin said the backing for a privately-funded centre was "almost certain to provoke a judicial review".
The Causeway attracts nearly 500,000 visitors a year. The previous visitors' centre on the site burned down in April 2000.
Renowned for its polygonal columns of layered basalt - resulting from a volcanic eruption 60 million years ago - it is the only World Heritage Site in Northern Ireland.