Even for an actor who has played a vampire-hunter with a guilty conscience, a Baltimore crime lord with a taste for Adam Smith, and an asset manager with a stalker, the role of the Norse deity Heimdall – guardian of the burning rainbow bridge between the world of men and the world of gods – was always going to be a bit of a challenge.

But playing a god in Kenneth Branagh's forthcoming film Thor has turned out to be the least of Idris Elba's worries, after fans of the comic books turned on the star of The Wire for reasons that have nothing to do with his acting ability and everything to do with the colour of his skin.

When news emerged late last year that the 37-year-old black Londoner had been chosen to play Heimdall, "the whitest of the gods", a being who can hear the sap flowing in trees and look across time and space, many devotees of the Marvel comics on which the film is based flocked to online forums to weep, gnash their teeth and unleash a tide of indignation.

A fortnight ago, the actor told Jonathan Ross that his take on Heimdall was "Norse by way of Hackney, Canning Town". And at the beginning of the month, he told a press conference that he saw his casting as an encouraging step.

His view was not shared among the more vehement of the comic books' fans. "This PC crap has gone too far!" wailed one. "Norse deities are not of an African ethnicity! … It's the principle of the matter. It's about respecting the integrity of the source material, both comics and Norse mythologies."

Fellow fans were quick to nod their horn-helmeted heads.

"At the risk of sounding like a bigot, I think this is nuts!" said another. "Asgard is home to the Norse Gods!!! Not too many un-fair complexion types roaming the frigid waste lands up there. I wouldn't expect to see many Brad Pitt types walking around in the [first mainstream black superhero] Black Panther's Wakanda Palace!"

Elba, who was born in Hackney, north-east London, to a Ghanaian mother and Sierra Leonean father, has addressed such concerns in a string of recent interviews.

"There has been a big debate about it: can a black man play a Nordic character?" he told TV Times. "Hang about, Thor's mythical, right? Thor has a hammer that flies to him when he clicks his fingers. That's OK, but the colour of my skin is wrong?

"I was cast in Thor and I'm cast as a Nordic god," he said. "If you know anything about the Nords, they don't look like me but there you go. I think that's a sign of the times for the future. I think we will see multi-level casting. I think we will see that, and I think that's good."

Elba, who shot to fame as the erudite and thoughtful gangster Stringer Bell in critically acclaimed US television serial The Wire, also used his interview with TV Times to warn viewers against pigeonholing his new BBC crime drama, Luther, just because it was about a black policeman.

"I think we'll put ourselves in a corner if we just describe Luther as a black detective," he said. "There haven't been many in the past, but the fact that he's black is neither here nor there."

The actor added that while it was "great to have a character who happens to be black in the central position … he still bleeds, just like anyone else".

Elba is working in the US and was unavailable for comment yesterday.

However, his publicist flatly dismissed any suggestion of a row between fans and film-makers, telling the Guardian that the actor was merely being mischievous. "There's no controversy," said Rupert Fowler. "Idris was being flippant in the [TV Times] interview."

His UK agent, Roger Charteris, said Elba had chosen the role of Heimdall on artistic rather than political grounds. "He just wanted to do the movie and work with Kenneth Branagh.

"He liked the script and he liked the movie and he had always wanted to work with Kenneth Branagh. It wasn't like a statement: 'Oh, I'm going to do this.' It's always a purely creative decision."

Or perhaps Elba was seeking to emulate his fellow British actor and Wire costar Dominic West. Last year, West – who has played the Ukrainian-Russian son of Pablo Picasso, a Spartan statesman and a French detective – revealed he had decided to accept the part of the Australian scientist Professor Howard Florey in a BBC TV drama about the discovery of penicillin, in protest against non-English actors playing famous English roles. "I was sort of smarting from Russell Crowe coming over here and playing Robin Hood and all these foreigners coming over here and stealing our great heroes," he said, his tongue lodged firmly in his cheek. "I felt I was striking a blow back by being a Brit playing a foreigner."

The Equality and Human Rights Commission said: "It's up to the casting director and producers to decide who is suitable for a role. It is not actually illegal to discriminate for authenticity purposes in the theatre. There is an exception under the Race Relations Act which says if it is required for the role, you can ask for someone of a certain colour."

Colour-blind casting: how cinema has lagged behind the stage

Idris Elba is not the first black British actor to play a Scandinavian icon. In 2001, Adrian Lester played Hamlet in Paris, receiving rave reviews for his portrayal of the melancholy Dane in Peter Brook's stripped-down production.

In the same year, David Oyelowo became the first black actor in the Royal Shakespeare Company's history to be cast in the role of an English monarch when he played Henry VI in Histories.

In 2002, colour-blind casting came to Noël Coward when Chiwetel Ejiofor played Nicky Lancaster in The Vortex at the Donmar Warehouse.

Lester, who played the lead role in Nicholas Hytner's satirical updating of Henry V in 2003, also joined the cast of the first all-black Broadway production of Cat On a Hot Tin Roof. Debbie Allen's take on Tennessee Williams's play, which opened in New York in 2008, starred James Earl Jones as Big Daddy and Phylicia Rashād as Big Mama. It transferred to the West End last November, with Lester as Brick, who was played in the 1958 film by Paul Newman.

Although the tradition of white actors such as Laurence Olivier and Orson Welles "blacking up" to play Othello has all but disappeared, gentile actors – such as Al Pacino – still routinely play Shylock in Shakespeare's The Merchant of Venice.

Cinema, which is far less reliant on existing, classic material, has lagged behind theatre when it comes to colour-blind casting.

Rumours of a black James Bond remain just that, although his CIA friend Felix Leiter has been played by two African-American actors, Bernie Casey in 1983's Never Say Never Again, and Jeffrey Wright in the Daniel Craig films Casino Royale (2006) and Quantum of Solace (2008).

In 1999, another originally white US lawman, Captain James West, was played by Will Smith in Wild Wild West, which also starred Kenneth Branagh.