The DUP is preparing to use a controversial mechanism at Stormont to prevent a Bill on integrated education from being passed.
The party has tabled a Petition of Concern in the Assembly ahead of the Final Reading of the Integrated Education Bill on Wednesday.
DUP MLA Diane Dodds has said it would be a "dereliction of duty to 93% of pupils in Northern Ireland" if other MLAs who are opposed to the "segregation and elevation of one sector of our education system" don't sign the petition.
Mrs Dodds described the proposed legislation as "bad law".
"I want to see children educated together but this Bill will penalise controlled and maintained schools because they have the wrong sign above the door not because of any failing with inclusion."
The Alliance Party's Kellie Armstrong brought the Private Members' Bill to the Assembly which would increase the number of integrated school places in Northern Ireland.
It would also place a legal requirement on the Department of Education to promote and reform integrated education.
Some principals in the non integrated sector have described the legislation as "unjust".
The Bill is supported by the SDLP and Sinn Fein, but the DUP strongly oppose it.
The DUP needs 30 signatures for a Petition of Concern which will mean the legislation can only pass with cross-community support in the assembly.
The DUP has 25 votes, but needs the support of others for the petition to be successful.
The party is looking to the UUP and other independents to support the move.
In a statement Diane Dodds added: "The stakes could not be higher. Claire Sugden and UUP MLAs have an opportunity to do the right thing."
Sinn Fein's Pat Sheehan has branded the DUP's action as a "shameful stunt".
He said: "It’s shameful that the DUP is trying to use the Petition of Concern to block a Bill on integrated education.
“The irony is, the DUP are using a mechanism which has not been deployed in this mandate in an effort to prevent children being educated together. This is yet another example of the DUP’s opposition to progressive change."
The use of the Petition of Concern has been criticised by some parties in the past, with the belief that its use was being abused. It has not been used since MLAs returned to Stormont two years ago.