In a poem he didn't publish in his lifetime, Ian Hamilton recounts a meeting with an eager but narcissistic American writer loosely based, it would seem, on James Dickey, best known for the novel Deliverance:

A six foot three American breathologist
Has cornered me for cocktails; "Suck on these,"
He says, and chucks me a slim vol.
Entitled: Big. Two words a line, at most,
Nine lines a page, typography diseased,
It's signed "To Ian, in pulse-harmony -
You dig? Love, Irv. November, seventy-three."
And on the sleeve, a photograph:
Irv felling trees.

A scrupulous critic, of himself as well as others, Hamilton was probably right to consider this a "Work in Progress" (that's its title) rather than the finished article. Still the poem has clearly been worked at: untypically for Hamilton, there's a loose rhyme scheme and a foray into light verse. Something more than a piss-take is going on, however. Irv may be comical - a pseud and phoney - but, in a poem which itself runs to nine lines, "nine lines a page" can't be accounted a sneer. In fact, despite their obvious differences, Ian and Irv are country cousins, on the one hand drawn to large gestures (and hard drinking), on the other stubbornly miniaturist in their verse forms. Even the male bravado of the last line has its muted suburban British equivalent when Hamilton, in another poem, describes a "trellis that needs fixing, that I'll fix".

Slight though it is, "Work in Progress" asks questions that preoccupied Hamilton throughout his life. How openly can I write about myself and others? How immodestly to pursue the grail of art? Most important of all, what to put in and what to leave out? "In certain moods I used to crave expansiveness and bulk," he once wrote, "and early on I had several shots at getting 'more of the world' into my verse: more narrative, more satire, more intelligence, and so on." But in the end he decided "to stop fretting and to keep the whole business of 'my poetry' separate from the rest of my so-called literary life." It was a purist choice, an eschewal of literary clutter in favour of poems that were intense and enigmatic. But Hamilton knew he was paying a price - that certain aspects of himself (worldliness, humour, irony) would never be expressed; that despite his ferocious honesty, the poems would give us less than the whole man.

"So-called", along with the quote marks round "my poetry", are characteristically self-deprecating. But insofar as they question the substance of Hamilton's achievement, they're wildly misleading. Few literary figures in the second half of the 20th century had his range. He was a brilliant editor (first of the poetry magazine The Review, then of the glossier New Review); an outstanding biographer (of Robert Lowell, JD Salinger, Matthew Arnold and - spot the odd one out - Paul Gascoigne); a high-minded arts presenter (of BBC2's Bookmark); a diligent anthologist; and the toughest, most intelligent poetry reviewer since Randall Jarrell. It wasn't just poets who benefited from his sardonic encouragement, but novelists and playwrights. What mattered most, though, were the poems, which came slowly at the best of times even without the distraction of a day job.

Just as friends liked to imitate Hamilton's wry, corner-of-the-mouth putdowns, poets impersonated his style. For a time, in the era of the Mini car and miniskirt, his mini-poems were the height of fashion. Hamilton was too level-headed to get carried away. But he couldn't ignore the burden of expectation. In another unpublished poem, "The Veteran", a "grey, hard-veined" survivor of an earlier war contemptuously asks him what he does: "I said I wrote / Three times before he got it. Then he leant / So close I took his rotten breath inside me / And asked 'What about?'; and he is right." A more confident poet might have given the veteran short shrift. But as an admirer of Keith Douglas, Hamilton respected the courage and gravitas of those who had fought in the second world war. The 60s might be fun, but compared with the 40s they were frivolous. "The Vietnam war drags on / In one corner of our living-room", one of his poems begins.

Yet Hamilton, no less than Douglas, did write about "true things, significant things". And burdened though he was, the best of his poems are marvellous for their unburdenings - for seeming to come out of nowhere ("miraculous lyrical arrivals") and to leave all the doubts behind. This is "Old Photograph": "You are wandering in the deep field / That backs on to the room I used to work in / And from time to time / You look up to see if I am watching you. / To this day / Your arms are full of the wild flowers / You were most in love with."

A photo records an instant but the person captured in this one looks up "from time to time", animated by the poet's memory. We infer loss - a broken relationship, a falling out of love - but can't be sure; there are no clues about the identity of the "you". The poem has an emotional force nevertheless: there's the pressure of all that hasn't been said as well as what has. All but three of the words are monosyllables, as if the poet were too choked to speak.

Hamilton's poems often address an unspecified "you", and are claustrophobically enclosed within a bedroom, sickroom or institution. There's a strange mixture of impersonality and intimacy - no names or giveaway details, yet a rapt attentiveness to hands, eyes, hair and skin. Thanks to a late interview Hamilton gave, and to Alan Jenkins's introductory essay, we now know that there were two "you"s: his father Robert, who died of cancer when Ian was 13; and his first wife Gisela, who suffered from a mental illness. Sometimes the two seem almost interchangeable: "our half-hearted love affair goes on", he writes of his father in "Epitaph". Sometimes the subject speaks up, and the you becomes the poet. Either way, the poems are uncompromising: maximum suffering, maximum control. Love and duty underlie the malaise. Whether it's his father or his first wife he's writing about, the motive is equally magical: to write a poem so perfect that it will heal the wounded or bring back the dead.

Hamilton knew that his poems were sometimes victims of their own stringency - that in omitting the biographical circumstances and restricting himself to a few sparse lines, he was asking too much of his readers. But he disapproved of writers such as Lowell, who exposed and exploited those close to them. And he trusted in the authenticity of the voice he had found, which was lusher, more romantic, more vulnerable and even "feminine" than his reputation as a literary bruiser suggests. In middle age, he relaxed a little and wrote at greater length. But the poems of that period, "Larkinesque" and "The Forties", are too self-conscious, too strewn with ironising quote marks, to be at ease with themselves. At some level, Hamilton thought that "true" poets are always young and in pain, and was discomfited by the comforts of middle age. He feared producing only "bruised rewrites of what I'd done before".

Some of his last poems, from the 90s, are brief, enigmatic and sorrowful, like his earlier ones. And where the "so-called literary life" impinges, it's to chilling effect. Here, in its entirety, is "Biography":

Who turned the page? When I went out
Last night, his Life was left wide-open,
Half-way through, in lamplight on my desk:
The Middle years.
Now look at him. Who turned the page?

At 50 Hamilton put together a selection of just 50 poems. Ten years later it was 60. He died at 63, and it was never likely that he would be one of those poets, like Larkin, whose oeuvre dramatically increases after death. Still, Jenkins has made a terrific job of assembling this edition, with 20 pages of uncollected and unpublished poems, an intelligent and moving introductory essay, and detailed notes on variant texts. There's no lost masterpiece here. But some of the stuff Jenkins has retrieved is fascinating: "Untranslatable", for example, which acknowledges the allure of obscurity in poetry ("it's what I can't grasp that draws me back"); and "Ties", a poem of exactly that kind, which ends: "Inside the house / He's playing genealogies again, / The usual curse / His, yours, theirs, everyone's. And hers." Of course it's disappointing not to have more but also, in another respect reassuring: Ian Hamilton was indeed his own best critic.

 Blake Morrison's latest book is South of the River (Vintage)