But this week Rother chief executive Derek Stevens told the Observer that no such instruction had been given.
The firm is charging £125 to release its clamps. Its action has caused consternation among regular users of Cooden's beach - popular with wind-surfers.
In a double blow, news of the parking ban comes as Southern Water has admitted in court a sewage leak which earned Cooden Beach national bad publicity. It was named by the Sunday Times as one of the country's most polluted bathing areas.
The clampers' action follows the recent removal of a traveller who had been illegally parked on the beach since last Christmas.
Though double yellow lines border Herbrand Walk, drivers have previously enjoyed unrestricted free parking by going off-road and on to the beach.
Now signs have gone up warning that part of the beach is in private ownership.
The unwary who have not spotted the signs have found themselves seriously out of pocket.
Five signs are sighted directly opposite the beach on a fence on the other side of the road, with only one on the beach, which is close to the shore and sighted in the middle of pole supporting a Rother Boat Lane sign.
The signs state that without a valid PCS (Parking Control Services) permit, cars will be clamped, and the following charges will apply: Clamp release fee £125, plus £35 per day; fixed penalty notice £85; tow fee £250; credit card surcharge £5.
Proprietor of PCS, Mario Ireland, said his company had been hired by the landowners of that section of beach.
He said: "Some of the beach is privately owned and the owners do not want cars parked there."
Mr Ireland said that the landowners are happy to let people continue to use the beach for recreational purposes.,
He said: "To be honest it came as a bit of a shock to me that anyone would park on a beach."
Asked whether he considered the location of the signs might be confusing Mr Ireland replied: "As with everything, there are planning issues - most people would assume the signs meant not to park on the beach."
The clamping signs have erected for a few weeks but Mr Ireland refused to comment on how many people had so far had their cars clamped.
He said: "I'm not at liberty to say."
Asked how motorists could obtain the necessary PCS parking permit, he explained that they would be issued by the landowners, for their own private use.
He also claimed that it was Rother District Council who had told the landowners to enforce the no parking rule on the beach.
But the Rother chief executive told the Observer: "While Rother has had dealings with the landowners of late in respect of the 'travellers' issue, I am not aware that at anytime have any of my colleagues asked/instructed the landowners to enforce a general no-parking rule on the beach."