The Hungarian State Opera has asked its white performers to attest they identify as African American to circumvent a rule by the Gershwin estate that only an all-black cast may perform the Porgy and Bess musical.

The company was scheduled to start an all-white six-performance run of the celebrated musical on April 5 despite already drawing controversy last year when it first put on the opera in the same way.

The Gershwin Estate, which manages the musical legacy of the late American composers George and Ira Gershwin, stipulates that this particular musical may only be performed by an all-black cast, as per the creators' wishes.

But Szilveszter Okovacs, the general director of the Hungarian State Opera has criticised the rule, arguing it makes it near impossible to perform the musical in Europe.

He branded the rule as "racist" and told Euronews: "I don't want to fulfil this condition."

"It's just not possible to do this [an all-black cast], you cannot decide who performs in a show based on the colour of the skin or their origin."

He confirmed to Euronews that there are no black artists in the company and said that the singers and actors are under no obligation to sign the declaration in which they attest they are of African origin — although 15 of the 28 performers have.

Hungarian news website Index reported that programmes in the opera's foyer state that the production "is unauthorised and is contrary to the requirements for the presentation of the work."

The company is also using illegal copies of the musical scores made last year before the sheets of music were recalled by the Gershwin Estate, a source told Index.

Porgy and Bess tells the story of Porgy, a disabled black beggar living in Charleston, in South Carolina, in the 1930s and his attempts to save Bess, the woman he loves.

A production of Porgy and Bess was put on at the English National Opera in October last year, featuring an all-black cast.

The Berlin Philharmonic put on a production in 2012 with black opera singers.