Theatre management has appealed to council bosses and the Scottish Government for help after learning of the extended closure yesterday.
Glasgow City Council confirmed the block in Sauchiehall Street gutted by fire in last Thursday’s blaze is to be demolished on safety grounds.
The properties affected are 92 to 106 Sauchiehall Street - from The Works stationery shop to Specsavers at the junction with Hope Street.
The blaze destroyed Victoria’s nightclub and engulfed the surrounding area in smoke.
Fire crews prevented the blaze from spreading to the 114 year-old Pavilion Theatre.
But staff have now been told it will be some time before the historic theatre can return to normal.
A statement issued on Monday night said: “This is indeed the saddest day we have had since the flood in 1992.
“After waiting to hear all day, we have just been advised by Glasgow City Council Building Control that we will be denied access to the theatre for around two months.
“After which, we will then be allowed in to ascertain the damage caused by the fire.
“Only then will we be able to carry out any works required.”
At the height of the blaze on Thursday morning, more than 120 firefighters were at the scene on the Glasgow city centre street, tackling flames an inferno on the roof of the building which houses Victoria’s nightclub.
The Scottish Fire and Rescue Service said it was one of the biggest incidents the service has had to deal with and officers remained at the scene over the weekend to damp down the site.
Glasgow City Council said the building could not be saved with demolition expected over the next two months.
The properties affected are 92 to 106 Sauchiehall Street - from The Works stationery shop to Savers at the junction with Hope Street.
The council said it has met with the building owners and shops in the block including Greggs, Specsavers and Victoria’s nightclub are dealing with insurers.
A council spokeswoman said: “An exclusion zone has been erected around the site of the dangerous buildings, which will be demolished as they cannot be saved.
“We have met with the owners of buildings affected by the fire, and will maintain this dialogue over the period.
“The owners of properties in the buildings to be demolished have met with insurers to discuss the next steps.”
An asbestos warning was issued to local residents and businesses as firefighters battled the blaze but atmospheric testing later found there was no risk.
No-one was injured in the incident, but shows at the Pavilion and nearby Theatre Royal were cancelled in the wake of the fire.
The Pavilion thanked emergency services for saving the “grand old lady” of Renfield Street, close to the fire.