DUP MP Gregory Campbell has launched a scathing attack on Sinn Féin over its response to the Covid pandemic.
The East Derry MP accused his party's government partners of placing "politics above public health".
Sinn Féin responded by saying the DUP had abused Stormont mechanisms to veto public health measures and was divided internally.
Mr Campbell's statement was issued by the DUP press office rather than his own Westminster account, indicating endorsement by the party leadership.
He was speaking as the DUP and Sinn Féin mark a year back in office following the New Decade, New Approach agreement, and five years to the day since Arlene Foster first became First Minister.
"From day one Sinn Féin has played politics with the virus," Mr Campbell claimed.
"They follow the science when it suits, break the rules asunder when it suits and tell the rest of us to 'do as we say not as we do'.
He listed nine episodes over the last 12 months as evidence, including early disagreement over the closing of schools and the funeral of Bobby Storey.
"The Sinn Féin story of the pandemic so far has been one of opportunism, exploitation and hypocrisy. Sinn Féin’s credibility in handling coronavirus is in tatters," he said.
"The advice being followed by Sinn Féin are the diktats issued by Connolly House rather than the vital public health messaging and united community approach that is needed."
A Sinn Féin spokesperson responded by saying: "We will take no lectures from a party that abused a mechanism to protect the rights of minorities to veto public health measures designed to protect the health service and its workers.
"Instead of attempts at division, we need ministers working together and focussed on public health rather than the interval divisions laid bare every day within the ranks of the DUP.”
Meanwhile, SDLP party leader Colum Eastwood accused both the Sinn Féin and DUP of having "failed the test of leadership after a year of crisis".
He said the his party continued to play its role in the power-sharing government but it only had one seat and the "dysfunction that engulfs the Executive will only ever be solved if the Joint First Ministers use their powers to fix it".
"For our part, the SDLP will always work with willing partners to deliver for our citizens but we will not cover the cracks in the dysfunctional and divisive relationship that come to define the Executive Office."
