Alarm has been expressed at the lack of a plan following the resurfacing of toxic blue-green algae on Lough Neagh, Northern Ireland's largest fresh water lake.
Earlier this month Stormont Agriculture and Environment Minister Andrew Muir called for the urgent signing off by the Executive on an action plan to tackle the issue.
It is understood to contain 37 actions, 17 of which needed Executive support.
Lough Neagh is the biggest freshwater lake by surface area in Ireland and the UK and it supplies 40% of Northern Ireland's drinking water. The lake also sustains a major eel-fishing industry.
Noxious blooms covered large parts of the lough last summer and also affected other waterways and beaches in the region.
Nitrogen and phosphorus from agricultural fertiliser running off fields is believed to be a major contributory factor.
The spread of the invasive zebra mussel species is also understood to have played a role, as they have made the water clearer, allowing more sunlight to penetrate, stimulating more algal photosynthesis.
Climate change is another factor cited, with the highest water temperature at Lough Neagh recorded last June.
Tthe Lough Neagh Partnership said with the visible impact of the blue-green algae returning, it is profoundly disappointed that a plan has not been signed off on yet.
Manager Gerry Darby said it is "no surprise" that the blue-green algae is "back with a vengeance".
"It was only a matter of time with the right weather conditions that it would reappear," he said.
"We consistently campaigned over the winter for action to be taken, as we feared that momentum would be lost once the algae disappeared below the surface and it would be a case of out of sight out of mind.
"We met with the main political parties and, despite assurances that immediate action would be taken upon Stormont's return, in reality we have not seen any of the promised efforts to resolve the crisis.
"Whilst we have put on record that we have welcomed the plan presented by Minister Muir, we are utterly disheartened by the lack of consensus to approve and implement it.
"As a result, we face another summer watching this ecological disaster unfold, powerless to intervene."
Read more: Journey to recovery in Lough Neagh crisis could be a long one
