The City of Edinburgh Council (CEC) has scrapped plans to reopen the city's Usher Hall amid an ongoing £20m revamp due to concerns that such a move could impact upon the project's scheduled completion in July.

Both the Scottish Chamber Orchestra (SCO) and the Royal Scottish National Orchestra (RSNO) were due to stage events at the venue in May, but delays to the refurbishment of the 95-year-old concert hall have meant that this is no longer possible.

The £20m project got underway in March 2007 to provide a new dedicated education space, enhanced protection of the venue's acoustics and improvements to access and circulation, including new staircases.

A new glass wing is also being created to house a café/bar, a new box office area and additional hospitality areas, while dressing rooms and other backstage facilities are being refurbished and extended.

Work was temporarily halted in summer 2007 in order for Usher Hall to be used during the Edinburgh Festival, before the scheme ran into delays as a range of difficulties with the construction site were identified. Work now looks set to continue uninterrupted until July, when the revamp is scheduled for completion.

CEC's culture leader, Deidre Brock, said: "These bookings were taken in good faith, but the project has experienced unexpected problems which have pushed up costs. The sums involved making the venue available and the potential impact on the project further down the line means that it's just not possible to hose these events."

RSNO chief executive, Simon Woods, expressed his disappointment at the decision. He said: "Needless to say that we are frustrated and disappointed that the re-opening has been put back, and that we are again being forced to change plans for concerts which we believed to be absolutely firm commitments.

"That said, it's an old and complicated building, and we will of course be patient as the council attempts to control what is evidently an extremely difficult construction programme."