Mr Ringland, who stood in 2010 as a UUP-Conservative candidate, said that in a straight fight between Naomi Long and Gavin Robinson, he could not vote for the DUP.
David Ford MLA said: “The remarks by Trevor Ringland have supported Alliance claims about the opposition that we are hearing on the doors from Ulster Unionists to the pact in East Belfast.
“The DUP have taken the voters in East Belfast for granted and assumed that Ulster Unionists would automatically transfer to them. Alliance believes that votes have to be earned through hard work, trust and experience.
“It is clear that the momentum is with Naomi in this contest as more people back her following her achievements over the past five years as well as the vision she has to build on the progress that has already been made.
“On May 7th, the public have a choice between Naomi who wants to take East Belfast forward or the DUP who want to take it back.”