A leading academic has warned of a growing gulf between British writers and their more ambitious, adventurous US counterparts as the newly named Bailey's women's prize for fiction included only four British authors among the 20 longlisted for the prize.

David Brauner, associate professor of English at Reading University, said British novelists were overly cautious and parochial compared with Americans, who had more nerve, more ambition and relied more heavily "on imagination and the power of language to create worlds that are unfamiliar".

On Monday, the inaugural winner of the Folio prize will be announced. Of its eight contestants, only one is British. "I think this is part of a larger trend and I think we'll see the Man Booker list reflect this inequity as well," said Brauner. "Contemporary American fiction is much more exciting and diverse and vibrant than British fiction, particularly English fiction. It has been the case for some time and I can only see the trend exacerbating – the gulf is becoming greater and greater.

"Oddly, I think the best British writers recognise the superiority of their American counterparts but seem unable to emulate in their own work what they admire."

Organisers of the Man Booker prize prompted lively debate last year when they announced they were opening up what had been a Commonwealth prize to all English language writers. There was a fear that US writers would take over.

But Brauner said the prizes were exposing a malaise in British writing that he had detected several years ago. "There's a cautiousness, a parochialism, a tendency to write carefully crafted, carefully researched fiction and a reluctance to be boldly imaginative. Even the best English fiction writers – Hilary Mantel is an obvious example – are very heavily reliant on historical research.

"In too much English fiction there is a reluctance to take risks. What the Americans do so well is just to rely more on imagination and the power of language to create worlds that are unfamiliar. They have got more nerve, more verve, more ambition. Most English writers don't have it to the same degree."

But what is the reason for that? Could it be the creative writing courses that Hanif Kureishi this week called "a waste of time"? Brauner said the courses were an American import but that British courses seemed to produce novels designed to "work well for readers who have been trained to read novels".

The chair of the Bailey's prize judges, Helen Fraser, chief executive of the Girls' Day School Trust and an ex-managing director of Penguin Books, said there was a preponderance of historical fiction this year – 57 of the 158 books they read – and a feeling that many "pulled in the historical background as a sort of prop rather than it being an intrinsic part of the fiction".

Fraser conceded there were fewer British writers on her longlist – there were seven last year and eight in 2012 – but did not feel it was a matter for too much concern. "This has always been a very international prize. I think it's just that every year brings a different crop of books."

That may be the case but the prize, formerly known as the Orange, has been won by a US novelist for the past five years.

The biggest names on this year's list are the Canadian Margaret Atwood for Maddaddam, the third novel in her sci-fi trilogy; and the American Donna Tartt for The Goldfinch, a doorstop of a novel that seems to have astonished and bored critics in equal measure.

Fraser said her panel was "gripped" by the novel, one that Tartt has been nursing and writing for 10 years.

There are seven US authors on the list in total. Fraser said her judges were particularly pleased to have so many writers at the beginning of their careers – six first-time novels and seven second novels.

"It is a very interesting, exciting, diverse and in some ways surprising list," she said. "We felt that each one of these books is one you could confidently put in somebody else's hands and say you will have a fantastic reading experience. You will really enjoy this book. Enjoyability is very high on the list."

The four British writers are MJ Carter for The Strangler Vine, a Victorian India romp; Deborah Kay Davies, for Reasons She Goes to the Woods; Charlotte Mendelson for Almost English and Evie Wyld for All the Birds, Singing set in both the rough Australian outback and an unnamed British island.

Two former Orange prize winners are in contention – the Nigerian writer Chimamanda Ngozi Adichie for her third novel Americanah; and the American writer Suzanne Berne for The Dogs of Littlefield.

The judging panel this year also consisted of the classicist Mary Beard, writer Denise Mina, and journalists Caitlin Moran and Sophie Raworth.

Jane Gardam, 85, is the only British contender in the Folio prize. Lavinia Greenlaw, chair of the judges, has said she believes a lot of English language fiction is being written too safely.

Brauner, who has published widely on contemporary fiction, believes that is true and that the British are more guilty. "It comes down to imagination and language. On a sentence-by-sentence basis American authors are writing more exciting and more daring prose and I don't know why that is. It is difficult to work out but there is something going on."

The Bailey's longlist

Chimamanda Ngozi Adichie Americanah (Nigerian, third novel)

Margaret Atwood Maddaddam (Canadian, 14th novel)

Suzanne Berne The Dogs of Littlefield (American, fourth novel)

Fatima Bhutto The Shadow of the Crescent Moon (Pakistani, first novel)

Claire Cameron The Bear (Canadian, second novel)

Lea Carpenter Eleven Days (American, first novel)

MJ Carter The Strangler Vine (British, first novel)

Eleanor Catton The Luminaries (New Zealand/Canadian, second novel)

Deborah Kay Davies Reasons She Goes to the Woods (British, second novel)

Elizabeth Gilbert The Signature of All Things (American, second novel)

Hannah Kent Burial Rites (Australian, first novel)

Rachel Kushner The Flamethrowers (American, second novel)

Jhumpa Lahiri The Lowland (Indian/American, second novel)

Audrey Magee The Undertaking (Irish, first novel)

Eimear McBride A Girl is a Half-Formed Thing (Irish, first novel)

Charlotte Mendelson Almost English (British, fourth novel)

Anna Quindlen Still Life With Bread Crumbs (American, seventh novel)

Elizabeth Strout The Burgess Boys (American, fourth novel)

Donna Tartt The Goldfinch (American, third novel)

Evie Wyld All the Birds, Singing (British, second novel)