The company behind a planned offshore wind farm said it has given back almost 80% of its development area.
The Navitus Bay project – for up to 121 turbines off Dorset, Hampshire and the Isle of Wight – announced it would hand the seabed back to the Crown Estate.
But Bournemouth council, which opposes the £3.5bn scheme, has dismissed the announcement as a “smokescreen”.
The Secretary of State for Energy and Climate Change is currently considering whether to grant permission.
The Planning Inspectorate has spent six months studying the plans, which developers say could power up to 700,000 homes when completed.
Navitus Bay said it had always promised it would not use the remaining parts of the development area to build a larger wind farm if the project gained consent.
The company said: “Today’s move, which will see decisions about this unused area being taken away from Navitus Bay, fulfils this promise.”
Responding to the announcement, leader of Bournemouth Borough Council John Beesley said it was “designed to draw attention away” from the scheme’s drawbacks.
He said: “Navitus Bay wants to develop one of the most environmentally sensitive parts of the seabed with a vast wind farm that is too close to shore and will severely damage the sensitive natural coastline and local economy.”
He added that the plans would risk almost 5,000 local jobs and cause a total economic loss of £6.3bn.
Andrew Langley, of campaign group Challenge Navitus, said the “so-called handing back” of unused seabed was entirely normal and of no significance.
He added: “It does not guarantee that the remaining seabed will not be used in the future for other energy projects or oil and gas exploration.
“We maintain [Navitus Bay] is too big and too close to the protected landscapes of Dorset, Hampshire and the Isle of Wight.”