The cost of reopening the Levenmouth line has been estimated at £20m
The leader of Fife Council has said opposition politicians are putting the Leven rail project in jeopardy.
Councillor Peter Grant said Labour members were engaged in "negative campaigning" at a time when the council needed to be presenting a united front.
He warned that such action could undermine attempts to reopen the line between Thornton and Leven.
It followed calls by the opposition for £2m of money set aside for the project to be ring-fenced by the authority.
Mr Grant said: "Everyone knows we are getting to a critical stage in our efforts to gain government approval for this desperately-needed service.
"In our submission to Transport Scotland we placed great emphasis on the fact that the rail link has unanimous cross-party support in Fife Council as well as the enthusiastic backing of the local constituency MSP and the Levenmouth community.
"But every time we think we have unanimous support, opposition politicians go behind our backs to the press with negative stories.
"This kind of co-ordinated negative campaigning is undermining the case for the rail link at a crucial stage in the process."
The Labour MSP Claire Baker recently urged the Scottish Government to press ahead with agreeing a structure plan for Fife. She said it was likely to cause delay to the rail project.
But councillor Tony Martin rejected the claim and said the scheme was fully on track.
Last week, senior Labour councillor Mark Hood called for a steering group to be set up to develop the proposal. This was also publicly rejected by the council.
Fife Council Labour leader, Alex Rowley, said Mr Grant appeared to be confusing petty politicking with legitimate debate.
He said: "We are advised that it is unlikely that the £2m will be spent and this is more of a gesture to the Scottish Government.
"What we are saying is there are transport issues in Levenmouth. The £2m therefore should be ring fenced to drive forward sorting transport problems."
The council leader said: "I am today publicly calling on all of Fife's politicians to stop this petty party politicking and give their unambiguous and unqualified support for a rail link which will play a vital role in the continuing regeneration of the whole Levenmouth area."