Northern Ireland faces financial penalties of £5million per month until the legislation is passed in the Assembly.
Stewart Dickson MLA said: “The SDLP and Sinn Fein both know that we have to implement the welfare reform legislation. They are unfairly and irresponsibly raising public expectations about what can be achieved.
“Parties need to be truthful with the public about the limited change we can actually make to the legislation, as significant alterations will incur massive costs that will have to be covered by reducing funding in other areas.
“A complete failure to implement the legislation will cost us £5million per month and leave us with the near impossible task of setting up our own benefits system.
“The Executive has achieved a number of significant concessions. The Social Development Minister must now bring forward the legislation and work with the Assembly Committee to find any further possible amendments and refinements in order to protect the most vulnerable members of our society. We can no longer leave this issue on the shelf.”