The National Union of Journalists' (NUJ) general secretary is visiting the corporation's Scottish headquarters today amid talk of industrial action and a threat to coverage of both the Commonwealth Games and the referendum.
Mr Robertson is understood to have been told his contract will not be renewed in August as part of cost-cutting measures, with senior NUJ sources warning of 'devastation' of staffing levels once this year's sequence of high-profile events has concluded and of plummeting morale.
It is understood Mr Robertson has taken legal advice on the cancellation of his "talent contract", which the NUJ says does not provide the same rights as regular staff contracts. His colleagues are threatening industrial action over the move, which has sparked today's meeting.
NUJ general secretary Michelle Stanistreet will lead the union's negotiations with BBC managers, a clear indication of how seriously the matter is being taken.
Asked why Mr Robertson was being axed, a senior NUJ figure said: "Who knows? Gary's probably the best presenter they've got. I'm assuming its something personal with senior management figures. The mood has shifted from incredulity to downright anger.
"Gary's taking legal advice. It's so serious the general secretary is coming up to lead the discussions. It also gets to the nub of the BBC hiring presenters on these so-called talent contracts instead of putting them on staff."
Mr Robertson has worked as a broadcaster with the BBC since 1990 and has become a key figure on Radio Scotland since 2000.
He took the helm at Good Morning Scotland as main anchor in 2006 and has also hosted Newsnight Scotland and the Politics Show Scotland.
News of his forced departure comes on the back of a poor first week for the BBC's new news magazine programme, Scotland 2014. The show, fronted by Sarah Smith, has been lagging way behind STV rival Scotland Tonight since it replaced Newsnight Scotland, with viewing figures as low as 22,000.
The NUJ source said staff had told him staff at BBC Scotland found the programme to be symptomatic of a culture of "dumbing down".
There has also been staff disquiet over the recruitment of London-based "big names" such as Jim Naughtie being parachuted in to present programmes on Radio Scotland with the financial situation as tight as has been claimed. Relations between BBC management and staff were already said to be strained in Glasgow before the Robertson decision, with spending around the independence referendum said to be a contentious issue.
An internal BBC survey had staff telling management they feel they are grossly under-resourced with claims of a culture of bullying. Staff are also believed to have decided to boycott internal appraisals, brought in by chief Ken McQuarrie, due later this year.
An NUJ spokesman said: "There is the real possibility of industrial action during the weeks through to and including September. We are already close to balloting on industrial action over problems with treatment of the staff.
"There is a huge amount of shock over Gary being dumped. He has worked tirelessly, often on long shifts, for 15 years and is a very talented broadcaster."
Last night, a BBC spokesman said: "We don't comment on contract negotiations with freelances. The meeting with the union is a general one and we have had no indication that possible industrial action will be discussed."