Published Thursday, 20 December 2012
Mr Harbinson and First Minister Peter Robinson. (© DUP)
Mr Harbinson quit Alliance earlier this year over its stance on gay marriage, eight months after being co-opted onto North Down council to replace Tony Hill, who passed away.
He attended the DUP's annual conference last month and on Thursday announced his decision to join the party.
Mr Harbinson said: "I believe the views of the Alliance Party on such issues are increasingly out of touch with the vast majority of people in Northern Ireland.
"Within North Down I have valued the friendship and working relationship with DUP Councillors and I was delighted with the warm welcome I was given as a guest at the recent party conference. I believe that the DUP provides a strong and united voice that can deliver not just for North Down, but for Northern Ireland as a whole."
Alliance group leader for North Down, Andrew Muir, said he's "astonished" by the move.
Mr Muir said: "I am astonished that Adam has decided to join the DUP. After recent events any move from the Alliance Party to the DUP is simply not credible.
"Whilst Alliance has remained steadfast in support of a shared future the DUP have whipped up tensions bringing us back to the old divisive politics of the past.
"Adam now has no moral authority to continue as a Councillor. Any integrity he had left has been destroyed by taking the seat of a long standing Alliance activist and handing it to the DUP."
Meanwhile the DUP leader has welcomed Mr Harbinson to the party.
Peter Robinson said: "I am delighted that Adam has taken the decision to join the DUP having recently attended our annual party conference. Adam has made his views known about the difficulties he had with Alliance policy and that he could not remain a member.
"I can assure him that he will find a warm welcome in the DUP."
© UTV News