The former Romany Café and car park at Grève de Lecq has been put up for sale, with an asking price of £5 million.
Deputy Lyndon Farnham - who represents St Mary, St Ouen and St Peter - is calling for Jersey's government to buy the site to keep it in public ownership.
He is calling for ministers to negotiate the purchase so it could be used in a way "that will be of benefit to the public".
Last year, planning permission was approved to turn the site into a luxury four-bedroom mansion and 100-seat café - but with a smaller car park than the one currently on the site.
While the site has been privately owned for years, islanders were able to use the car park when visiting the beach.
Estate agents Wilsons Knight Frank have the property listed for sale with an asking price of at least £5 million in its current condition, or over £11 million if the site is redeveloped in line with the current plans.
Deputy Lyndon Farnham is calling for Jersey's government to purchase the site to stop the redevelopment
Deputy Farnham said: "I think it's really important to the States to buy this site, to protect the bay, to protect the character of the bay, to ensure there is good public access to the bay by maintaining the car and coach parking and to ensure we don't allow such vital parts of our coastline to disappear forever into the likes of large single dwellings.
"I think the risk right now is very real, it's owned by a private developer, who has planning permission for just that", he added.
But the Deputy said it isn't too late: "There is still an opportunity for the States to buy it because the property is on the market for sale and I think it's a good time now to negotiate and see if we can strike the right deal."
States members will vote on whether to enter negotiations for the site - and if the Deputy's plans are approved, the assembly will also get a vote before the purchase is agreed.
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