The disused track between Uckfield and Lewes is overgrown
Campaigners have pledged to continue their fight to reopen a stretch of railway despite a report concluding it would not be economically viable.
The results of a Network Rail study on the seven-mile Lewes to Uckfield line carried out for local authorities were revealed on Wednesday.
It said that reopening the line was technically possible but not economic.
"We are not surprised, but this is a blip - it is just the start of the fight," campaigner Brian Hart said.
The track between Uckfield and Lewes was closed in 1969 because it was thought increased road building made it obsolete.
No further work
The Wealden Line Campaign group argues that traffic congestion now means it should be reopened.
They said it would relieve pressure on the adjacent Brighton Main Line by opening up another route between London and the south coast.
Trains currently only run north from Uckfield.
The Network Rail feasibility study, which has been delayed several times, was prepared for a board comprising local councils, MPs and the South East England Development Agency and Regional Assembly.
"There is a lot of professional expertise contained in the study and the board is satisfied that Network Rail has covered all the relevant issues," said chairman councillor Rupert Simmons.
The board said no further work was proposed on the project unless there were significant changes to government transport policy.
"We hope local people are not too disappointed," said Mr Hart.
"We think this is a skewed study - it is absurd to say there is no economic case for reopening the line.
"We are going to scrutinise the report and we think we can made a strong business case."