The French port owners want to build a new berth and slipway, and deepen a channel to upgrade facilities.
Businesses have welcomed the economic benefit but Sussex Wildlife Trust object to the loss of shingle habitat, and residents have said they will lose their only remaining sandy beach.
Newhaven Port and Properties have not commented to the BBC.
Helen Macaulay, from the town's chamber of commerce, said Newhaven needed more businesses and more jobs, and local concerns about infrastructure were being dealt with by the port.
The plans include a nature reserve but Ian Hepburn, from Sussex Wildlife Trust, said the development would damage coastal shingle and species there including reptiles, invertebrates, breeding birds and plants.
Former town councillor Rod Main said West Beach had already been closed by the port and this expansion would see the town lose its one other remaining area of sandy beach.
Calling for West Beach to reopen, he added: "This company are just taking away every sandy beach we've got."
A report submitted to Lewes council said the plans would help to regenerate Newhaven and create jobs, and the expansion would provide overspill space for the new Rampion wind farm.
Officers said it was an opportunity to create a modern port, and the benefits outweighed harm such as the loss of sandy beach, impact on surf conditions, and effects on ecology and archaeology.
The plans will be considered later.
Expansion plans put forward by Newhaven Port have been recommended for approval by Lewes councillors.