Agriculture Minister Edwin Poots has been criticised for preventing another north-south ministerial meeting from taking place.
The DUP is boycotting some North-South Ministerial Council (NSMC) meetings due to its opposition to the NI Protocol.
Wednesday's meeting was billed as "long-standing meeting" relating to agriculture.
Nichola Mallon, Stormont's infrastructure minister, criticised Mr Poots for his absence.
Mr Poots is one of two candidates running to become the next DUP leader, with the election due to take place on Friday.
He has already pledged to take more measures against the protocol, and is also seeking to take legal action against it.
Ms Mallon said if his absence from Wednesday's scheduled meeting was "a sign of things to come, it doesn't bode well".
"Power-sharing requires leadership," she added in a tweet.
The SDLP has said it will raise Mr Poots' non-attendance with the executive as well as the Irish and British governments as a matter of urgency, adding "Edwin Poots doesn't get to pick and choose which responsibilities and legal obligations he wants to uphold".
Refusal to engage
The NSMC is the main body for cross-border co-operation between the governments of Northern Ireland and the Republic of Ireland.
Under the DUP's five-point plan in protest at post-Brexit arrangements for Northern Ireland, ministers are refusing to take part in north-south engagement where the protocol is being discussed.
Last week, the outgoing DUP leader Arlene Foster did attend a rescheduled north-south meeting with Ms Mallon and her Irish counterpart.
But it is understood some of those who supported the move to oust Mrs Foster from office were concerned about the party's involvement in north-south discussions.
The Irish and UK governments have agreed to hold a high-level joint conference next month.