The move, revealed in the SNP’s Holyrood election manifesto, comes a month after the last coal trains used the line to Longannet Power Station near Kincardine before the plant’s closure.
It will be welcomed by campaigners calling for the freight route to be used to provide direct trains between Dunfermline and Glasgow.
The SNP manifesto stated: We will examine the case for an extension of the Stirling-Alloa rail line to Dunfermline by upgrading the existing Longannet freight line.”
The Scotsman understands that although the single-track route is still in place, improvements would be required for it to take regular passenger trains for the first time in 86 years.
These include to the ride quality, which is lower for freight trains.
The Dunfermline-Longannet section was used by coal trains to supply the power station from the east until the Stirling-Alloa-Kincardine line was re-laid in 2008, which provided access from the west.
ScotRail trains use the line only as far as Alloa.
Re-opening the rest of the route to Dunfermline could now create a “Forth Circle” like the Fife Circle line between Inverkeithing, Lochgelly and Kirkcaldy.
A station could be re-opened at the historic village of Culross to improve access for tourists.
The Kincardine-Dunfermline line closed to passengers in 1930 but is used by occasional steam charter trains.
Paul Tetlaw, a rail campaigner for public transport lobby group Transform Scotland, has said: “It would be the perfect opportunity to build on the huge investment of constructing the route through Alloa to Kincardine, by creating a passenger service.
“It would open up the north bank of the Forth to all sorts of new travel possibilities, such as to the delightful village of Culross, and also provide access to both Glasgow and Edinburgh for work and leisure.”
A spokesman for the ScotRail Alliance, which includes track owner Network Rail, said: “We are always open to discussing proposals to enhance the railway if they have a viable business case and meet a clear need.”