A £200m bid to buy the port of Dover as a "people's port" has been dismissed by the harbour board as "totally unrealistic and undeliverable".
Dover Harbour Board (DHB) said Dover People's Port Trust (DPPT) was making promises it could not deliver.
Dover residents have been told they can become members of DPPT for £10.
Dover MP Charlie Elphicke said: "This is a serious bid backed by serious people. They wouldn't waste their time if it was unrealistic."
The people's port was launched on 30 October on Dover beach at an event attended by singer Dame Vera Lynn.
Representatives from three ferry companies were also there, along with the leader of Kent County Council Paul Carter and Conservative MP Mr Elphicke.
Funding for the bid in excess of the contribution from Dover residents would be raised in the City of London.
'Gateway to nation'
DHB said in a statement on Monday the plan was neither a commercial nor a business proposition.
DHB, which has run the port as a trust since 1606, asked the government for permission to privatise it in January. A decision is expected soon.
Dover People's Port website says it wants to prevent the "gateway to the nation" being sold to overseas buyers.
But DHB said the people's port promises were unaffordable.
"Despite making statements that the people of Dover would 'own' the port - at a minimal payment of only £10 per head- it is estimated that such ownership could only be achieved if each and every one of the people of Dover, 39,000 in all, contributed over £5,000 per head to the trust," it said.
"The reality is that financial institutions would be financing the deal."
It also said the proposal made no allowance for the required £85m investment in the Eastern Docks or the £250m needed to build a new terminal.
"The reality is that the DPPT is a political instrument," it said.
Mr Elphicke added: "I am sorry that they are being so negative about the community's bid.
"It is backed, as everyone knows, by major British banks, by the ferry companies and by substantial businessmen.
"The privatisation plan under their idea would mean millions (of pounds) for management.
"My proposal is that we have millions for the people of Dover."