Campaigners have called for a new rail link connecting the north and south Strathclyde networks to be made an "urgent priority".
At present, passengers have to walk between stations
Business leaders, transport experts and politicians have joined together to launch the Crossrail Glasgow project.
The £120m scheme would build a line crossing the city centre, connecting stations in the north and south.
The Transport Scotland agency, which advises ministers, said it still needed evidence of the project's benefits.
Passengers travelling through Glasgow currently have to walk between Central and Queen Street stations to transfer.
Crossrail would allow people from Edinburgh and the north of Scotland to travel direct to Ayrshire, Inverclyde and Glasgow Airport without having to change trains.
The proposed link would close the gap over the River Clyde connecting stations in the city's north east with those in the south west and would involve laying 2km of new track.
A new station would be built at Glasgow Cross and High Street station would be moved further east.
MSPs have already approved a new rail link between Glasgow city centre and the airport.
Strathclyde Partnership for Transport (SPT) which is behind the Crossrail campaign, said it would allow people from the east and north of Scotland to travel directly to both Glasgow and Prestwick airports.
Councillor Alistair Watson, chair of SPT, called for the Scottish Parliament to treat Crossrail as a priority when members return after the 3 May elections.
He said: "Crossrail opens up the whole railway network to the west of Scotland and the greater Glasgow area and - once the new rail link is completed - to Glasgow Airport."
Dr Lesley Sawers, chief executive of Glasgow Chamber of Commerce, said: "Crossrail is essential to keep Glasgow competitive and to ensure that the transport structure is in place to support Glasgow and the west of Scotland's ambitious growth plans."
Transport Scotland is the agency of the Scottish Executive responsible for carrying out the rail and trunk road powers of Scottish ministers.
A spokesman said: "SPT have so far shown Crossrail is technically possible but as yet, need to provide evidence of how the scheme would benefit passengers or how many would use it."
He said they were working with SPT to establish information and a business case for consideration alongside other schemes looking for funding.
Bill Butler MSP, convener of the Scottish Parliament's Cross Party Group on Crossrail, said the link should take priority over a more expensive cross-city tunnel.
"Already Crossrail has been delayed for far too long. Some commentators continue to argue for a tunnel under Glasgow.
"However, any continued investigation into this option will be damaging and pointless."
Sir Menzies Campbell MP, John Scott MSP, Nicola Sturgeon MSP and Frank McAveety MSP are among the politicians supporting the campaign.