Regeneration chiefs in East Sussex have attacked plans by Eurostar to cut the number of international trains stopping at Ashford International by two thirds.
Ebbsfleet International Station will take up many of Ashford's services
East Sussex County Council and Hastings Borough Council said they were horrified at the decision.
They fear the cuts could undermine efforts to boost jobs and tourism.
It was revealed last month that the Kent station will lose its Brussels and off-peak Paris services when the new Ebbsfleet station opens next October.
Eurostar said Ashford would retain some peak daily services to Paris and weekly trains to France, while also running high-speed domestic services from 2009.
But in a joint statement, the two authorities said it was a major setback to long-term plans to boost local economy through rail connections.
"We want to see Hastings and East Sussex become the European gateway for the south coast, and to attract new businesses to the area which could take advantage of the access to international markets.
"The news also undermines the good progress made in upgrading and improving the line between Ashford and Hastings."
Ebbsfleet International Station in Kent is 34 miles (54km) further north than Ashford - a drive of one and a half hours from Hastings, as opposed to approximately 40 minutes on the train direct from Hastings.
The councils said the decision went against the South East Plan and they would be writing to MPs and the transport minister to raise their concerns.
Eurostar denied the transfer of services signalled the end for Ashford International.
"The Ashford station will remain there, it's still part of the Eurostar network but it will sit alongside Ebbsfleet," a spokesman said.