First has announced plans to overhaul its bus network, calling the new scheme "SimpliCITY".
Now Strathclyde Partnership for Transport (SPT) chairman George Redmond, has spoken out about the revamp, saying he has concerns about cuts to lesser-used services.
He said: "First's consultation with passengers and other stakeholders is an encouraging step, however we are concerned that services which are considered less commercially attractive could be put at risk.
"We believe the primary focus of bus services should be customer need and increasing patronage.
"A 'pick and mix', or rather 'simpliCITY' approach will only disadvantage those who depend on bus the most."
Graeme Hendry, leader of the SNP opposition on Glasgow City Council, has also weighed in on the new plans, saying First need to extend the consultation period, which finishes on March 1.
He has also appealed to SPT to get more involved in the process.
He said: "Instead of just sitting back, SPT needs to step in and use their quality bus corridor powers.
"With First Bus I am also concerned that their business model seems to be about cutting services and raising prices, as opposed to investing in local routes."
Paul Rooney, Labour councillor for Garscadden and Scotstounhill, said the proposals, specifically the planned axing of the No 11 route, will have a "terrible impact" on the community, .
He said: "People in Knightswood and Yoker are reliant on the service. Scrapping the No 11 will have a terrible impact in those communities and that impact will be felt most keenly by older residents and the most vulnerable."
Meanwhile, Greater Pollok Councillor David McDonald said some of the changes First are proposing are "positive" but said parts of his ward have no bus service whatsoever.
He added: "Some of people here must walk 20 or 30 minutes to catch a bus.
"I think this is because they are not 'big money' routes."
Ronnie Park, Managing Director, First Glasgow, said: "Our proposals are not set in stone.
"We have laid out what we believe to be exciting plans that will deliver improved bus services. We are asking people to tell us what they think, before we finalise those plans.
"SPT was consulted in advance of our public consultation and we look forward to further discussion with them."