A Sinn Féin motion calling for new equality legislation was defeated due to unionist opposition in the assembly last week.
The motion from Foyle Assembly member Martina Anderson encouraged the executive to bring forward a bill to harmonise existing laws.
The DUP immediately opposed the motion and were joined by the UUP to defeat it by 45 votes to 42.
UUP assembly member for Strang-ford David McNarry said after the debate that the difference of opinion between DUP First Minister Ian Paisley’s party and Deputy First Minister Martin McGuinness’s party signalled the unravelling of cooperation between them.
“I think what we saw today was jointery going out the window. This is a crisis in the Office of the First and Deputy First Minister at the first hurdle,” Mr McNarry said.
Mr McGuinness said he intended to take proposals for fresh legislation to the executive as soon as possible.
East Derry DUP Assembly member Gregory Campbell defended his party’s decision to oppose equality legislation, insisting that it could damage the interests of Protestants.
“It is not the principle that we have the problem with but the way that equality legislation has been implemented here in the past,” he said.
Mr Campbell said previous equality legislation had “discriminated” against Protestants, such as the requirement for balanced recruitment into the civil service and police.
“The legislation before led to an Equality Commission that was supposed to protect equality but it did the opposite and not only defended, but actually promoted, discrimination by endorsing the 50/50 recruitment for the police which meant that Protestant applicants were being turned away,” he said.