The Ulster Unionists have done a deal with Sinn Fein to prevent the DUP getting the top position in Craigavon Council for the fifth year in a row.
The DUP hit out yesterday after the UUP banded with Sinn Fein and the SDLP to hand the republican party the deputy mayor position in the borough.
Ulster Unionist Colin McCusker was elected as mayor with the help of Sinn Fein and the SDLP.
In return UUP councillors voted for Catherine Seeley over the DUP's Darryn Causby for deputy mayor.
Ms Seeley was at the centre of a sectarian intimidation storm recently when she left her teaching post at the Boys' Model in north Belfast after threats from loyalists. UUP councillor Arnold Hatch queried why the DUP refused to back Mr McCusker for mayor, accusing it of greed.
The DUP hit back, with its leader on Craigavon Council Carla Lockhart accusing the Ulster Unionists of "childish hatred".
"A deal was concocted between the UUP and Sinn Fein to keep the DUP out in the final year of Craigavon Council," Ms Lockhart said.
"The UUP's childish hatred for the DUP was manifested when the UUP group chose to vote for a Sinn Fein deputy mayor rather than supporting my DUP colleague.
"This latest self-serving step by the UUP demonstrates that the UUP is more about opposing the DUP than about opposing republicans.
"For 25 consecutive years when the UUP was the largest party in Craigavon they never supported a DUP mayor once, yet they now bend over backwards to support Sinn Fein."
Ms Seeley said she felt her election was a "very positive decision".
"I think we have to focus on the positive message that was turned out for the first time for Craigavon Borough Council," she said.
Meanwhile, a farmer who became famous across the world for ordering pop star Rihanna to cover up has been selected to lead the new North Down and Ards council.
Alan Graham was nominated by the DUP to act as presiding councillor at its first meeting yesterday morning.
In 2011 Mr Graham was horrified when the singer staged a raunchy video shoot in his field near Bangor, Co Down.