Local residents and businesses have described their ongoing exclusion from homes and premises around the Glasgow School of Art’s Mackintosh building as “tortuous”, amid growing calls for a public inquiry into the cause of the second blaze to devastate the building in four years.

Nearly two months on from the fire that gutted “the Mack” on the night of 15 June, there is growing anger and frustration at the lack of any timeline for re-entry for those whose properties remain inaccessible. But Tom Inns, the school’s director, has told the Guardian that he hopes the security cordon, imposed by Glasgow city council building control as the painstaking work to stabilise the remaining structure continues, will be reduced in a fortnight.

Gill Hutchison, owner of Biggars music store, which has traded from premises within the cordon for a century, speaks for many businesses when she questions the length of time the work is taking. “From the beginning, we were told that the Mackintosh building was at imminent risk of collapse and would be demolished. Now we’re told its about the stabilisation of the building, which implies a much longer-term process.”

Hutchison, who estimates that she has lost at least £120,000 in business and relocation costs since the fire, adds: “The feeling emerging among the businesses is that the cordon is no longer about public safety but to allow high-access equipment to move freely. We’re feeling very low, because there isn’t an end in sight. It’s tortuous for people.”

Paul Evangelista, who owns Absolut Hair and Beauty, considers himself fortunate to have found a temporary site just outside the cordon, but has spent thousands on restocking and advertising that his salon is still open, while discovering that his business interruption insurance is void because there is nothing technically wrong with his original premises.

At the end of July, over a month after the fire, the Scottish government announced a £5m fund for affected businesses. But Evangelista points out that while immediate aid is welcome, most insurers will simply knock it off their final payout. ”

Engineers dismantling the unsafe sections of the Mackintosh building estimated that the process, which began on 10 July, would take eight weeks. They also insist that controlled dismantling is the only way to prevent damage to surrounding properties. As one source close to the project puts it: “We understand why people wanted us to bring in a wrecking ball, but that would only make things worse.”

As well as about 350 business owners and staff, an estimated 67 local residents remain unable to return to their homes. While all have now been rehoused and given a hardship grant of £3,000 from the Scottish government and Glasgow city council, there have been complaints about the quality of the temporary accommodation.

Adrian Nairn, who speaks for the Garnethill Displaced Residents Group, asks: “Imagine being told to leave your home in the clothes you’re standing up in, in the middle of the night, and not come back for eight weeks, bearing in mind that you might need medication or hearing aids that you’ve left behind in the rush, or that you might be going on holiday because it’s the summer, and need your passports.”

Nairn is calling for a public inquiry not only into the cause of the fire, but also the subsequent crisis management and the legality of the cordon itself.

The Scottish fire and rescue service gives no timescale for its investigation, but says that it is processing a “significant volume of information”, adding: “Access to the site is presently restricted but, when declared safe, our specialist investigators will be able to gain access with a view to establishing the circumstances surrounding this incident.”

Glasgow city council insists that local residents and businesses are its first priority.

A spokesman said: “We fully understand the desire that residents and businesses have to get back into their properties as soon as possible – and to know, now, when that will be. If we could possibly answer that question with any certainty, we would. However, the building remains in a perilous condition and the work being carried out by GSoA’s contractors is complex and dangerous.”

“Our building control experts are monitoring the work and, as it advances, they expect to learn more about the condition of neighbouring buildings – which will be crucial in determining when it will be safe to return to surrounding streets.”

Inns said: “We are working seven days a week to make the building stable as soon as possible ... The shoring scaffolding on Dalhousie Street, which is the critical part of the work to make this east gable safe, is on schedule for completion in the next two weeks. After that we hope very much that Glasgow city council building control will be able to reduce the size of the security cordon.”

Stuart Robertson, director of the Charles Rennie Mackintosh Society, believes that a public inquiry is now essential, although he acknowledges the fire may well have been so devastating as to make the discovery of its cause impossible.

He also questioned why there had not been more definitive answers from Kier, the construction company contracted to carry out the restoration after the 2014 fire and still in control of the building when it again caught fire in June.

It emerged soon after the second blaze that there were no operational sprinklers at the site but a Kier spokeswoman said a fire strategy had been in place, which included a smoke and heat detection system, 24-hour security and fire patrols by a team of three guards.

While Inns, has committed to rebuilding the Mackintosh as a working art institution, Robertson believes that project – which is likely to take up to a decade – should be overseen by an expert panel rather than the school’s management. “Their prime purpose is to teach, and this is too big a project, so we need an expert panel to take that forward. And it would be hard for them to raise funds because people would say, ‘Could this happen a third time?’”