Alongside other sensual and macabre authors - Poe, Baudelaire, Swinburne - sits one of the most curious figures of English decadence, Ernest Dowson, whose centenary falls this week.

One imagines him a century ago disconsolately surveying the wreckage of his life. Yet the poems still captivate, winning him a loyal following with their emotional directness. They conjure up a world of plaintive distress, concentrating it in powerful bursts of lyrical verse: "They are not long, the weeping and the laughter"; "Beyond the need of weeping, beyond the reach of hand"; "I would not alter thy cold eyes"; "You would have understood me, had you waited"; "I have been faithful to thee, Cynara, in my fashion".

This was the real thing, a man steeped to the soul in poetry. Some of his lines were, as his friend WB Yeats said, destined for immortality, "bound to outlive famous novels and plays and learned histories and other discursive things". He was right. Dowson went into the language, giving us "Days of wine and roses" and "Wine and woman and song", plus - in "Gone with the wind" - the title of a classic film.

Dowson wrote 120 poems, some of which he refused to have published in his lifetime, as if they contained truths too painful to reveal. His companions of the 1890s - Wilde, Yeats, Symons, Beardsley, Gray, Johnson, Rothstein, Smithers - described his life as a human sacrifice to art, propelled by the "swift, disastrous and suicidal impetus of genius". He was "a desperate gamester who had risked all on one throw and lost". To critics, though, he represented "the sentiment, the sentimentality, the nerveless effeminacy... among the wreck of all that is mouldy and unwholesome".

Some people, such as Aubrey Beardsley, who illustrated Dowson's books, found the poet intolerable - dirty, diseased and drunken. Dowson was certainly a man easier to love than to like. When drunk he was, according to his friend Arthur Symons, "almost literally insane, certainly quite irresponsible... a vocabulary unknown to him sprang up like a whirlwind; he seemed always about to commit some absurd act of violence". Oscar Wilde, when asked why he spent his time with such a drunk, replied that it was unfortunate not that this poet should be drunk but that more drunks were not poets.

Dowson was a man of febrile sexual energy: when he could afford it he would have a woman (mainly prostitutes) each night. Yet he was also always described as gentle and drifting, with "the air of being submerged in a dream... the charm of an uncommon simplicity and sincerity". He had the power to attract and keep friends who never doubted his remarkable qualities, for all his faults.

Dowson had more qualification than most for finding himself listed among what Yeats called the "tragic generation". His family was not poor when he was born, but became increasingly impoverished throughout his childhood as they travelled around continental resorts in an attempt to cure his parents' tuberculosis. He had scant education, and was at last forced to work in the near-bankrupt family dry-dock business in Limehouse, pursuing literature as a sideline.

First his father and then his mother committed suicide; Dowson himself developed tuberculosis to add to his depression and his alcoholism. When Wilde was disgraced and imprisoned with hard labour, the best hopes of the decadent movement of which Dowson was a major figure were destroyed.

Dowson never had a relationship with a woman who could be considered his equal in intellect or age; he fell in love with Adelaide, the daughter of a Soho restaurant proprietor, when she was 12 and he was 22. Most of his best work was dedicated to her - "you, who are my verses" - but the over-sensitive poet was no kind of partner. Eventually, after six years of courtship and despite an offer of marriage, she married the family lodger who sometimes worked as a waiter in the restaurant.

Dowson, "suffering the torture of the damned", took to wandering, in Brittany, Paris and London. In 1900, at the age of 32, he died - of years of neglect as much as of tuberculosis - in a friend's house, owning nothing but his tattered manuscript book of verse. He was the last of the romantics.

• Jad Adams's biography of Ernest Dowson, Madder Music, Stronger Wine , is published by IB Tauris at £19.95.