The national advisory body for theatres has urged Croydon Council to reconsider controversial plans to completely close Fairfield Halls for redevelopment.

The Theatres Trust has written to the council to express concerns about the loss of expertise and audiences resulting from the two-year shutdown for a £30m revamp.

Simon Thomsett, chief executive of the venue, last year said he feared it would struggle to regain audiences and might never re-open unless parts of the building remained open during the work.

The council says complete closure would cut the cost of the redevelopment by £4.5m.

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But the Theatres Trust, a non-departmental public body sponsored by the Government, described it as "unfortunate" that the council had opted for a full closure.

Ross Anthony, the trust's planning advisor, said in a letter sent on April 5: "It is... unfortunate council has been unable to agree to a staged refurbishment, keeping part of the Halls open during the wider construction period to maintain some level of cultural offer for local residents.

"The loss of existing expertise and audiences puts incredible pressure on the new operators to rebuild that audience base upon reopening, further affecting the venues’ long term viability.

"We encourage the Council to reconsider this decision."

Fairfield Halls is due to close from mid-July until summer 2018 to allow for the redevelopment, which the council has promised will transform the theatre complex into a world-class venue.

Fairfield (Croydon) Ltd, the charity that runs the venue, eventually agreed to the closure in February after initially opposing it.

But the plans have been met with fierce opposition from campaigners, opposition councillors and staff, who have also raised concerns about a lack of certainty or clarity about who will run the Halls when the re-open.

Mr Anthony said Theatres Trust welcomed the council's "overall objectives... to modernise and refurbish Fairfield Halls to strengthen it as the key cultural destination in the region".

But he added: “The Trust is concerned the scheme is being advanced, and significant capital has been committed, without the involvement of a theatre/venue operator. 

“The Council must be sure the scheme meets the needs of the end user, particularly if a commercial operator is to be sought otherwise the viability of the Halls in the long run may be compromised. 

“The Trust strongly recommends a new operator is selected, or the existing operator is retained, and is involved in the design before proceeding with the scheme."

A Croydon Council spokeswoman said: “We will be contacting the Theatres Trust in response to their offer of support to us of an advisory peer review and welcome their involvement as a key national organisation that can help us develop the best possible future for Fairfield Halls.”