The SDLP's Mary Bradley said a DUP petition of concern regarding proposed amendments to the Caravans Bill, "made a bad situation worse", on 25 January 2011.
The petition of concern meant that the amendments would need the support of a majority of both nationalist and unionist MLAs.
The debate on the consideration stage of the bill centred on the licensing of travellers' sites.
Three amendments to the bill would have removed the right of local councils to license these sites.
Social development committee chairperson Simon Hamilton of the DUP said there had not been proper consultation on the issue.
He said he did not think the amendments dealt satisfactorily with the issues of travellers.
Mr Hamilton said that the original bill had nothing to do with travellers and their inclusion emanated from a submission from the Human Rights Commission.
The sponsor of the bill, John McCallister, and his UUP colleagues also opposed the grouping of amendments.
Mr McCallister said the Caravans Bill was not the correct vehicle to introduce such important legislation but he would abstain from the vote as he disagreed with the DUP's use of a petition of concern.
Anna Lo of the Alliance Party voiced her support for Mrs Bradley's comments and said it was a "shame" that the DUP had brought forward a petition to try to defeat the amendments.
The amendments were also supported by Sinn Fein but fell on a cross-community vote.
Other amendments brought by Social Development Minister Alex Attwood were supported in the assembly.