Network Rail expects to shut the Winchburgh Tunnel for 44 days while engineers carry out electrification work to the line.
The work would be carried out in the summer, with connections using other routes. Reports say the closure may occur in 2015.
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Campaigners Rail Future hit out at the move and called for a new line to be built bypassing the tunnel which would avoid any need for services to be disrupted.
But Transport Scotland says that the work will only take 44 days to complete and will cut journey times across the central belt.
The Edinburgh Glasgow Improvement Programme (Egip) electrification of the main line between the two cities should be completed by the end of 2016.
A Transport Scotland spokesman said: "Network Rail have confirmed they expect the closure to last around 44 days - significantly less than the 12-week period reported, and will be carried out in the summer months with all rail connections maintained via diversionary routes.
"We will be working with our rail partners to bring the 44 day closure in further still and will keep passengers updated on progress."