Peter Robinson and Martin McGuinness have been criticised as it emerged ministers are facing a gap of almost three months between Executive meetings.
The Belfast Telegraph can reveal the Executive is not due to meet again until Thursday, September 19 – after the First and Deputy First Ministers return from their latest US jobs mission.
But their office has also confirmed the last meeting was on July 4, a gap of exactly 12 weeks.
It also means the first Executive meeting will come after the Assembly's opening plenary session – next Monday – and the start of the Richard Haass talks due to begin on September 16.
During a summer of upheaval over parades in north Belfast, the republican commemoration in Castlederg and the DUP's U-turn on the Maze Peace Centre project, ministers did not meet.
With the Assembly's business committee due to meet today to agree on an agenda for the opening plenary sessions, there were claims the 12-week hiatus at Stormont Castle is the longest yet.
UUP leader Mike Nesbitt said: "I think given the summer we have had they should have been meeting. Given that we are trying to encourage collegiate government, 12 weeks without meeting is a powerfully long gap. It's nearly a quarter of a year.
"No doubt ministers have continued to pursue their own briefs but that is only half of what I think people expect. The other half is a sense of the parties working together to try to manage their difficulties and agree policies on the economy, education, health and housing."
Mr Nesbitt, who chairs the Stormont committee which monitors the First Ministers, added: "There should be a mechanism which would enable the other ministers to meet without the First or Deputy First Minister present."
The SDLP's Pat Ramsey said: "Given the heightened tension over the summer, it is unacceptable that the Executive has not met in almost 12 weeks.
"The political process has soured considerably and it does not seem credible that we have to wait until September 19 for the Executive to convene.
"People need to see strong leadership and political maturity emanating from the Executive table, not childish spats. They are fed up with the hypocritical mudslinging by the DUP and Sinn Fein (with) a rift between the First and Deputy First Minister exacerbated by letters from America and commemoration speeches."
And Alliance MLA Chris Lyttle added: "I am concerned at the length of time between meetings over the summer."
Dates in Stormont diaries
July 4 – last meeting of the Executive
July 12 – Orange parade banned in north Belfast
August 11 – IRA commemoration in Castlederg
August 14 – DUP U-turn on Maze centre
September 19 – next meeting of the Executive