Gray said: "The decision to cut GARL and 1300 jobs is a savage blow to the west of Scotland.
The GARL plan was included in the original bid when Glasgow was awarded the 2014 Commonwealth Games.
He added: "The decision not to reinstate the key GARL
transport project, and all the economic and environmental benefits that would bring, is particularly disappointing.
Scottish Chambers of Commerce chief executive Liz Cameron said: "In our view, the GARL project could be affordable.
The letter states: "The GARL project is not only desirable but affordable.
Finance Secretary John Swinney dropped the pounds 200million GARL
scheme - and 1300 jobs - last month.
Half of the pounds 400million GARL
scheme will go ahead.
Finance secretary John Swinney axed the pounds 200million GARL
project - which was intended to link Glasgow Central station to the airport via Paisley - when he unveiled his budget plans last month.
The link, known as GARL, will be scrapped even though it helped secure the 2014 Commonwealth Games for the city.
Scrapping GARL will save pounds 170million, finance secretary John Swinney said as he outlined his pounds 35billion budget for 2010-11.
In the meantime, the decision to scrap GARL - a key part of Glasgow's winning 2014 Commonwealth Games bid - has been widely condemned.
But projects such as GARL are too important to be used in a game of political brinkmanship.