"Yes, London is no longer the centre of poetry," Hugh Kenner tells us near the end of A Sinking Island: the modern English writers (Barrie & Jenkins, £16.95). It is a point he has hinted at pretty strongly for 250 pages, but he can restrain himself no longer. Only Charles Tomlinson, "England's chief living poet", and Basil Bunting keep us visibly afloat - only just. Looking back to the 1940s he names in brackets poets who rose against the "classicism" of Auden: "(Henry Treece, G.S. Fraser, George Barker, Vernon Watkins; and who are they?)" Dylan Thomas "seemed not to notice" the "machine world, which outraged Lawrence."

It's sad that Professor Kenner did not take the trouble to find out who Barker and Watkins are, or take into account that by the time Dylan Thomas came along there wasn't much point in "outrage" about machines, though Thomas does show in poems (not the anthology pieces, perhaps) machines in action and the human and urban consequences of technology. If Thomas's late pastoral is over-sugared and Time swings a trope and not a blade, there are prosodic epiphanies from which even a severe reader could allow himself to take a little pleasure, a little wonder.

Hugh Kenner's book is illuminating and vexing. It would be more illuminating if it were less vexing. On the one hand he is trying to give an account of this century's literary decline, especially the decline of readership; on the other he is out - as if on behalf of Pound and Ford, Lewis and Lawrence - to take his revenge on England, and specifically on London, to demonstrate that the literary culture which alienated or ignored such figures doomed itself to unseriousness and a fading marginality. How right he is - in part. But he, too, practises a crude metonymy, he judges a part and condemns the whole.

One feels chastened, but then questions arise: how are the great modernists faring in America - faring, that is, outside the Universities? Where is Pound's third and fourth generation progeny of writers and how do they measure up? Has Lewis found readers in a country which closed its ears to Robinson Jeffers? How well is Lawrence read? Why is Eliot still resented, and not only by the disciples of Williams? Are there heirs to Ford who have the accomplishment and range of Greene or Burgess?

How are the great modernists faring, for that matter, in Australia, New Zealand, in India, in South Africa, in Canada? Have they found anywhere, except in the imaginations of a diaspora of writers and readers, a comprehending audience (outside the academy)?

The virtue of Kenner's book is in its castigation of a limited and limiting readership, self-perpetuating, self-impoverishing, which has lost the language in which to address Pound or Lewis, Ford or Lawrence, and which either domesticates them by misreading or rejects them out of hand. The vice of this book is its stridency, for the rejection or misreading of the modernists is not limited to England; and many a writer who believes himself "emancipated" by the moderns goes off the rails dramatically - in ways which are not sanctioned by his exemplars, which those exemplars would have found risible.

If we look more narrowly at England, we find writers at work who have learned radical lessons from the modernists, and if Kenner - and other influential critics here and abroad - troubled to find out "who they are" - Barker, Graham, Sisson, Davie, Middleton, Gunn, Hill, Harrison, Fenton etc. - they might feel less depressed on our behalf. Even Larkin, despite his public utterances, was learned in the most unexpected areas. He had read, yes, the French Symbolists, Laura Riding, and even - Ezra Pound, read them. Contemporary British poetry is not all Raine and Motion, as Kenner seems to fear. Even Raine and Motion have more mileage in them than 'Raine' and 'Motion'.

Kenner writes persuasively about London, its decline, our decline. For 200 pages he is enlightening: yes, the relations between reader and writer are crucial, and bad readers can make for bad or alienated writers. It may well be that we have lost the necessary common language of value and judgement, a language we cannot recover unless we recover community. Perhaps we have grown deaf to the sounds the great moderns made. But I would contend - on the evidence of the contemporary English-language literatures that wash up on our shores - that we are not alone in this, and if our island is sinking, so too are the Antipodes, and a few land-masses even larger and more populous.

Away with nationalisms: they mar our criticism, they hinder the urgent dialogue that this book should give rise to.