A row has erupted over the origins of a play at the King's Head Theatre that producers claim is an Oscar Wilde “world premiere”.

Constance, which opens tonight (15 September 2011, previews from 13 September), is billed a “world premiere of the only unproduced Oscar Wilde play”, and is based on a French translation of a manuscript Wilde is thought to have written after his release from prison in 1897 and given to an American actress, Cora Brown Potter.

But speaking to Channel 4 News, the playwright's only grandson Merlin Holland dismissed these claims as “complete tosh”. He also told the Guardian he believes the play to be “a pretty appalling piece of work”.

Holland believes the translation, by Wilde enthusiast Guillot de Saix, was based only on a synopsis and not a complete manuscript.

“The existence of the synopsis is the only thing we know for certain”, he told Channel 4 reporter Matthew Cain. “He is known to have said to his friends in later years in Paris, 'I've lost the will to write'.”

In reply, the play's producer Adam Spreadbury-Maher said that, based on the evidence of letters and journals, he believes a “significant majority” on the play is Wilde's. “He breathes throughout the play – it is Oscar Wilde”, he added.

Constance centres on the wife of a rich industrialist, whose attempt to host an evening of entertainment at a country house is jeopardised by her extended family and aristocratic friends. Directed by Marc Urquhart, it continues until 23 October.