Environmental groups have rejected Shell's plans to decommission the Brent oilfield in the North Sea.
The groups claim the oil giant's proposals contain "insufficient information" and could breach international rules.
Shell has lodged plans with the UK Government's Department for Business, Energy and Industrial Strategy to decommission four of its platforms, and has asked for permission to leave the concrete legs of three of them on the seabed.
The firm said the safety risks associated with trying to remove them outweigh "minimal environmental benefit".
A 60-day consultation on the proposals ends on Monday.
WWF Scotland, Greenpeace UK, the Marine Conservation Society, Friends of the Earth Scotland, Kimo, Whale and Dolphin Conservation, the Scottish Wildlife Trust and RSPB Scotland have submitted a joint response.
The organisations say that Shell has not provided enough detail on its plans.
WWF Scotland director Lang Banks said: "Despite over 3,000 pages of documentation, it has not been possible to come to a view on Shell's decommissioning proposal due to insufficient information being provided by the company across several key areas.
"The internationally-agreed Ospar rules set out very clear criteria and procedures for operators to follow in carrying out such assessments, but we do not believe they have not been fully adhered to in this case.
"The material presented cannot be clearly cross-referenced to the Ospar requirements, meaning we cannot assess whether or not there is a solid case for the derogations sought by Shell.
"We are therefore left with no choice but to reject Shell's plans in their current state and have asked for key further information in order to adequately assess their proposals."
Ospar is the mechanism by which governments co-operate to protect the marine environment in the North-East Atlantic.
Mr Banks added: "Given the enormous size of the rigs and the iconic nature of the Brent field, its decommissioning is being watched closely, both here and globally, and it should therefore be aiming to set the highest possible benchmarks for the rest of the industry to follow.
"If done right, it could open the door for this country to lead a new multibillion-pound, global decommissioning industry that could create thousands of jobs as we continue our transition away from fossil fuels."
A Shell spokeswoman said: "Shell welcomes the feedback which has been received from stakeholders and members of the public during the 60-day public consultation period for the Brent field.
"The consultation concludes today and, over the coming weeks, we will continue to review and respond to the comments received."
Green MSP Mark Ruskell said: "Today's warning from numerous environmental groups about Shell's plans must be taken seriously.
"Cleaning up the legacy of the Brent oilfield is a chance we cannot afford to miss.
"The four platforms and associated miles of pipelines are on a much bigger scale than the Brent Spar project, which saw public condemnation, boycott and direct action against Shell when they tried to sink a redundant rig.
"Big oil already receives generous public subsidy to extract a resource we know we have to start leaving in the ground.
"It would be wrong for this same industry to be allowed to walk away from a situation that could create jobs and protect the marine environment we all rely on."