Stars including Brian Cox and Alan Cumming have issued a plea to save an Edinburgh theatre at risk of closing over increased costs for a vital redevelopment.

They have joined calls to save the King’s Theatre on Leven Street after it emerged that costs for refurbishment are likely to be 20-30% higher than the £25 million originally budgeted.

Unless the funding gap can be closed, then the theatre may be at risk of shutting as facilities must be brought up to modern access standards.

The venue is a “vital” part of the Edinburgh International Festival, says actor Brian Cox, who is an honorary patron of the theatre.

Alan Cumming performed as Roberts Burns in Burn at the King’s Theatre this year (Tommy Ga-Ken Wan/PA)

“It’s in August that we are reminded how vital the King’s Theatre is to the Edinburgh International Festival which over the years has played host to Juliette Binoche, Fiona Shaw and, this year, Alan Cumming and Gabriel Byrne,” he said.

“Without the planned, transformational redevelopment improving access, preserving heritage and opening the building up to the community, the King’s will close its doors forever.

“After a hugely successful fundraising effort to reach the original budgeted cost of £25 million, we cannot let the rising costs due to inflation, trade agreements and global conflict put the project in peril. We must save the King’s for future generations.”

Alan Cumming, who performed as Robert Burns in Burn at the festival this year, said the venue could do with a facelift.

Fiona Gibson says the theatre could close forever without additional funding (Greg MacVean/PA)

“The King’s Theatre is integral to the cultural health and wellbeing of the people of Edinburgh, and indeed Scotland. It brings us together in the winter via the annual pantomime and it welcomes citizens of the world every August during the festival.

“This year, I was back at the King’s with Burn and it reminded me how much I love this old beauty. Please, urgent funding is needed to help preserve the magic of the King’s.”

James Thieree, star of Room, presented at the King’s as part of Edinburgh International Festival this year, said the theatre felt like a “vessel that’s been on the sea for many years”.

He added: “I feel theatres like these are the real temples today – of the mind, of the imagination – and they have to be taken care of, cherished and protected.”

Externally the King’s Theatre will look largely the same after the planned redevelopment (Capital Theatres/PA)

Fiona Gibson, chief executive of Capital Theatres, said the project was in peril due to delays in the supply chain and increasing levels of inflation.

She said: “We estimate that the project costs will increase by between 20% and 30%.

“We’ve examined our options and we cannot reduce the project cost any further by value engineering and to delay the redevelopment could lead to even higher costs in the long-term, putting the entire project at risk.

“If this funding gap is not closed before December 2022, the last opportunity for us to give the go-head, the King’s could close its doors forever.

“Nearly all the original capital cost estimate of £25 million to transform the King’s is in place thanks to grants from the Scottish Government, City of Edinburgh Council, the National Lottery Heritage Fund; generous donations from our patrons and donors, companies and trusts; as well as Capital Theatres’ own contribution and our recent Crowdfunder.

“We are incredibly proud of the collective effort to reach this figure.”

Ms Gibson said the group were in “close contact” with original funders and hoped to secure additional support to ensure that the development can proceed as planned.