Legal thriller looms as Sherlock takes his caseload to New York

Benedict Cumberbatch, left, and Martin Freeman (BBC)

It's a fresh take on Sherlock Holmes which will transplant the sleuth to a modern-day setting. But it doesn't take Baker Street's finest to deduce the source material for a major new drama announced by American network CBS.

The producers of the BBC's acclaimed Sherlock series, starring Benedict Cumberbatch, are prepared to take legal action against the US network over a rival Holmes series which appears to tread on familiar ground.

The BBC version is already a cult hit in America, where it is screened on the PBS network. The show's contemporary reinvention of Sir Arthur Conan Doyle's stories, allied to slick production values, impressed network executives at CBS – so when an offer to remake the BBC's Sherlock for US viewers came to nothing, they decided to go ahead and make their own.

In a move which has caused concern at Hartswood Films, the BBC show's producers, CBS has commissioned Elementary, described as a new Sherlock Holmes adaptation set in modern-day New York.

Sue Vertue, Sherlock Executive Producer at Hartswood Films, said: "We understand that CBS are doing their own version of an updated Sherlock Holmes. It's interesting, as they approached us a while back about remaking our show. At the time, they made great assurances about their integrity, so we have to assume that their modernised Sherlock Holmes doesn't resemble ours in any way, as that would be extremely worrying." She added: "We are very proud of our show and like any proud parent, will protect the interest and wellbeing of our offspring."

Conan Doyle's creation has been subject to numerous screen incarnations, including Guy Ritchie's all-action Hollywood version. Holmes' sleuthing skills and character quirks also inspired House, Hugh Laurie's medical detective.

But it is Elementary's relocation of the character to a modern setting which may closely impinge on the BBC series, which has made laptops and text messaging an important element of its plots.

Margaret Tofalides, a copyright specialist at law firm Manches, said: "The concept of a new Sherlock Holmes is unprotectable. But if the unusual elements of the BBC series – the modern settings, characters, clothes, plots and distinctive visual style – were closely reproduced in the CBS version, that could form the basis of a potential copyright claim."

An American Sherlock could threaten the revenues returned to BBC Worldwide from the Cumberbatch show. The episodes have found an international audience through DVD sales and iTunes downloads.