SINN Féin chief Martin McGuinness has accused the DUP of doing a U-turn on the welfare bill.
Now his party plans to oppose the passage of the welfare bill in the assembly after Mr McGuinness said the DUP were “acting in bad faith” on the issue.
The Sinn Fein MP said the DUP had reneged on its commitments in the Stormont House Agreement to protect the most vulnerable people in society.
The five main parties reached a broad agreement on December 23 on a number of key issues, including welfare reforms.
The deputy first minister said: “At Stormont House the five parties agreed a series of measures to protect the vulnerable and safeguard current and future welfare claimants under the control of the executive.
“However, the DUP have acted in bad faith and are now reneging on their commitments to protect the most vulnerable.
It is their intention to provide only partial protection to current recipients of benefit and no protection whatsoever for future claimants.
“That is totally unacceptable.”
He said Sinn Féin was now issuing a petition of concern.