Black and Asian authors in the UK say they are being shoehorned by a publishing industry which is almost blindingly white into writing fiction that conforms to a stereotypical view of their communities.

Interviewed as part of a major new piece of research into diversity in publishing, the award-winning novelist Bernardine Evaristo was scathing in her indictment of the British books world. “Three decades ago, few novels were published by Britain’s Black and Asian novelists, while 20 years ago, a breakthrough occurred that became a short-lived trend,” said the author of Blonde Roots, a novel that flips history to put whites in the role of slaves. But “for the past few years, we have seen a return to the literary invisibility of the past, concealed by a deceptive tokenism.”

Children’s laureate Malorie Blackman agreed. “Over the last three or four years, I seem to have gone back to being the sole face of colour at literary or publishing events,” she says in the report. “What happened?”

The Writing the Future report, commissioned by writer development agency Spread the Word and to be launched at the London Book Fair on Thursday, found that the “best chance of publication” for a black, Asian or minority ethnic (BAME) writer was to write literary fiction conforming to a stereotypical view of their communities, addressing topics such as “racism, colonialism or post-colonialism as if these were the primary concerns of all BAME people”, said the report’s author Danuta Kean.

Even though the books market today is dominated by mass-market fiction, 42% of respondents from a BAME background wrote literary fiction, compared to 27% of white writers, the report found. Crime, by contrast, one of today’s biggest selling genres, only accounted for 4% of BAME novelists’ output, compared to 16% of work by white writers.

“Writers find that they are advised by agents and editors to make their manuscripts marketable in this country by upping the sari count, dealing with gang culture or some other image that conforms to white preconceptions,” writes Kean.

“Black and Asian authors complained that they were expected to portray a limited view of their own cultures or risk the accusation of inauthenticity if their characters or settings did not conform to white expectations. Failure to comply, many felt, limited their prospects of publication.”

Some writers reported turning to overseas publishers to find a deal, after failing to find understanding or a home for their work in the UK. Others said they made changes requested by publishers in order to get their work published, or submitted to publicity campaigns focusing entirely on their ethnicity. “I remember being told to make sure one half of a love relationship was white, because white readers would have problems reading books with ‘foreign’ settings or all-black casts,” one author, who chose to remain anonymous, told the researchers.

Only 47% of BAME writers had a literary agent for their debut, the survey found, compared to 64% of white novelists, while once a career was launched, 53% of BAME authors were agentless, compared to 37% of white writers. Kean said that “the importance of who you know and not what you know in publishing”, coupled with “the reliance on Oxbridge for recruitment”, combines to discriminate against unpublished BAME authors “who are less well represented in those institutions and therefore less likely to network with those who may help with their career”.

Writing the Future surveyed and interviewed more than 200 authors, of whom 30% came from a BAME background, and more than 100 publishing professionals for its report. It is the first large-scale, in-depth look at diversity in UK publishing in 10 years, but despite the raft of initiatives that addressed the “disturbing evidence of institutional bias” revealed in 2004’s In Full Colour report, “an old mono-culture still prevails” in publishing, said director of Spread the Word Sue Lawther, with things “as bad, or possibly even worse, than we imagined”.

One bestselling respondent described the publishing industry as “awash with white middle-class men at board level, many of whom see no anomaly in this or realise that it doesn’t reflect society as a whole”. Award-winning writer Aminatta Forna told Kean that “there is an orthodoxy whereby the presumed reader is totally mono-cultural, white middle England”, whereas “we know from looking at census data that this is a very outdated view”.

According to the report, BAME communities are expected to represent 30% of the population by 2050, with their current disposable income at an estimated £300bn.

Talking to publishers, researchers found that most estimated that up to 8% of their workforce self-identified as coming from a BAME background. Access to more definitive results was difficult to realise, as data was either not kept or not shared with researchers. “At times it was incredibly difficult for our experienced researchers to gain access to honest conversations with staff within the publishing industry. Many people didn’t want to speak on the record; a warning sign that something is wrong,” said Lawther.

Of the publishers and literary agents interviewed by Writing the Future, 74% of those employed by large publishing houses and 97% of agents described the industry as only “a little diverse”, or “not diverse at all”.

Literary festivals were also subjected to scrutiny in the report, with researchers looking through the more than 2,000 names appearing at Edinburgh, Cheltenham and Hay last year. Just 100 – 4% – were classified as people who were black Caribbean, black African, south Asian or east Asian, and UK-based.

“The past 10 years of turbulent change affecting the UK book industry has had a negative impact on attempts to become more diverse,” writes Kean. “Traditional publishers have retrenched and become more conservative in their editorial and employment choices. Nowhere is this more obvious than in the rise of the unpaid internship as a primary route into the business – a practice that immediately discriminates against those without the economic power to support living and working in London unwaged.”

She warns that if the trade does not become “less homogenised”, it “risks becoming a 20th-century throwback increasingly out of touch with a 21st-century world”.

The report ends with a series of recommendations, from banning unpaid internships to a newly formed industry-wide diversity scheme insisting on internal audits for members to address cultural bias.

Evaristo called it a “call to action aimed at a literary industry which has the power to get our stories out there, in our own words, because our stories need and deserve to be heard too.”

• This article was corrected on 15 April 2015 to say that BAME stands for black, Asian or minority ethnic, not black, Asian or Middle Eastern