Irvine Welsh, the author of Trainspotting, lashed out at the "highly imperialist-orientated Man Booker prize", whose winners have alternated "between largely upper-middle-class English writers and citizens of the former colonies, presumably to stamp legitimacy on this 'global accolade'".

Speaking at the Edinburgh international writers' conference, he added that the organisers' failure to refute accusations of anti-Scottishness, already voiced by Scottish writers such as Alan Bissett, was a sign of "arrogance" and "intellectual enfeeblement".

Welsh, who is famous for using Scottish dialect in his novels, said: "The Booker prize's contention to be an inclusive, non-discriminatory award could be demolished by anybody with even a rudimentary grasp of sixth-form sociology."

The award, he said, was "based on the conceit that upper-class Englishness is the cultural yardstick against which all literature must be measured".

Welsh was speaking on the third day of the five-day conference, held at the Edinburgh international book festival. The event is a restaging of the famous 1962 Edinburgh writers' conference when Rebecca West and Mary McCarthy snarled at each other; the then unknown William Burroughs – who was staying with Alexander Trocchi's doctor so they could both be amply supplied with heroin – sprang on to the international literary scene; and Muriel Spark said very little except what was icily to the point.

Welsh, giving the keynote address at the session on nationalism, said that the rise of globalised culture meant it "would be difficult for Trainspotting to be published today by a London-based publisher. The market has become much more defined and Trainspotting doesn't fit into any defined slot."

In a wide-ranging debate on localism, regionalism and nationalism in literature – without the near-fisticuffs that characterised the 1962 version, but with passionate applause for writers' statements and a certain amount of barracking against Ian Rankin's chairing of the session – Glasgow-based author Ewan Morrison argued that universalism, the great ideal of the postwar world, had been most effectively harnessed by global capitalism, and must at all costs be fought against. As Bissett put it, "protectionism for local cultures is sometimes necessary".

But Ben Okri, who won the 1991 Booker prize for The Famished Road, contested the terms of the argument, quoting Wole Soyinka's statement that a tiger doesn't debate its "tigritude"; it just pounces.

Okri continued: "The writer writes. As well as they can, as truthfully as they can from the depth of their spirits … If you say this space is Scottishness, you have limited the possibilities of Scottishness for all time … if you overdefine what is a national literature you will constantly reproduce a cycle of cliches."

The previous day's debate on style versus content saw the work of EL James condemned as "fucking dangerous" by poet Nick Laird, and "mental vomit" by poet and essayist Kapka Kassabova.

The session was kicked off by novelist Ali Smith with a virtuoso provocation: style, she said, was a kind of roaring with life. "Style … makes what's being told," she said. "A story is its style."

But could style – think of James Joyce – make books inaccessible? Bissett said: "I worry how style can exclude. You think about the people who are not convinced by literature and find it for a small elite … Style risks become fetishised and it becomes stylish people talking to one another."

China Miéville disagreed: the argument "risks being patronising", he said. He added: "If we try to second-guess readers it's a fool's game … Our job is not to give readers what they want, it is to try to make readers want what we give.

"Increasingly one reads books that are beautifully put and rather bloodless and anodyne. And I would much rather read an honourable failure than a dishonourable success, particularly in the case of style."

The Argentinian writer Carlos Gamerro agreed: "Three cheers for difficult writers who write for other writers!"

The first session had raised the question: should literature be political? Ahdaf Soueif, the Egyptian novelist and essayist, said it was too soon for her homeland's revolution to be fictionalised.

"A truly imagined and felt novel of the Egyptian revolution? I don't see how it can be done," she said. When the novelist was wrapped up in activism, the space and time and nuance for fiction could not emerge, she argued.

Okri agreed: "When your house is burning, your first job is to put the fire out: you don't write as a way of putting out the fire."

Miéville said that the contents of a work could be overstated. Because the novel was a commodified art form (like it or lump it) various avenues of "cultural performance" were made possible; when Iain Banks's calling for a cultural boycott of Israel in 2010 was a powerful act, even though "he writes about space ships" and not Palestine.

It was left to the Chinese poet Xi Chuan to question the idea of the moral purpose of the novel.

"We are taking it for granted that we are all good people, kind people, as we talk about this topic. But another question might be: should literature be fascist? Should be literature be Stalinist?

"There are hidden meanings here. Should literature be something that expresses your values, to show that you are a good or a kind person?"