Most biographers choose their subjects out of admiration, or curiosity, or a feeling of affinity. Carmen Callil is an exception. She regards the man at the center of “Bad Faith” (Alfred A. Knopf, 608 pages, $30) with a contempt that burns on every page.

Louis Darquier de Pellepoix, the Vichy official in charge of “Jewish questions,” who was directly or indirectly responsible for the deportation of 70,000 French Jews to Auschwitz, was an evil and disgusting man. Ms. Callil’s indignation is especially marked, because she did not really choose to write about Darquier. Instead, Darquier violently inserted himself into Ms. Callil’s existence, in an oblique but terrible way.

Ms. Callil writes in her prologue that for seven years she worked with a London psychiatrist named Anne Darquier. With her help, Ms. Callil, an expatriate Australian, recovered from a suicide attempt and “started to live in the world, like other people.” It is easy to imagine the shock she felt when, in September 1970, Anne died of an overdose of alcohol and pills, in one of those suicides that seemed not quite deliberate but also not quite accidental. From scattered hints in their conversations, Ms. Callil knew that Anne was deeply alienated from her parents: “There are some things and some people you can never forgive,” she once remarked. But it was not until a year later, when Ms. Callil happened to see “The Sorrow and the Pity,” the landmark documentary about Occupied France, that she connected her thoroughly English-sounding doctor with Louis Darquier de Pellepoix, the Vichy functionary shown “trotting up to Reinhard Heydrich … to shake his hand respectfully.”

The disclosure that the woman she trusted to help her live “like other people” was imprisoned in a legacy of almost unique horror prompted Ms. Callil to start thinking about the book that now, 36 years later, has taken shape as “Bad Faith.” (In the interim, Ms. Callil became a leading figure in British book publishing, notably as the founder of the feminist Virago Press.) These origins help to explain the unusual structure of “Bad Faith,” which combines a biography of Louis Darquier with a wider analysis of French fascism and collaboration, all the while keeping track of the childhood of Anne Darquier. This mélange means that “Bad Faith” is not totally lucid as an account of Vichy France and its political culture. But it is also what gives the book its compelling humanity, and helps Ms. Callil to bring out the full grotesqueness of Louis Darquier’s story.

Grotesque, rather than monstrous or terrifying, is the right word for Darquier. While he was an important figure in an evil regime, he was also a buffoon — a braggart, con man, drunk, womanizer, and embezzler. He achieved notoriety in the 1930s by trafficking in anti-Semitism, with all the demented ingenuity of Nazi propagandists like Julius Streicher. Among the things he believed, or said he believed, were that Jews used the bindings of the Talmud to smuggle cocaine into France and that Jews had rigged the French “Miss Cinema” competition to prevent a Christian from winning. Even Pierre Laval, the Nazi stooge who served as prime minister under the Occupation, thought that Darquier was “a fanatic and a madman.”

Yet as Ms. Callil shows, even Darquier’s anti-Semitism was less a true belief than a kind of grift, a confidence trick that succeeded beyond his wildest dreams. One of the clearest measures of the bankruptcy of fascism was the caliber of person who thrived under its dispensation. Nazi Germany was run by a collection of bankrupts, sadists, and crooks, and Darquier was their spiritual brother. Before he became famous on the nationalist right, he was the kind of man whose family refused to mention his name. Born in 1897, he fought with distinction in World War I, but his behavior after the armistice led to his dishonorable discharge from the army: “In peacetime he has not lived up to the hopes founded on his wartime behavior,” his final report noted. Like many fascists, Italian and German as well as French, he would spend the rest of his life trying to re-create the desperate fraternity of the front, the only place he had ever distinguished himself.

Certainly civilian life did not suit Darquier. While one of his brothers followed their father into the medical profession, and the other became a successful businessman, in 1925 Louis was fired from his job in a wheat brokerage for embezzling 500,000 francs. For the next nine years, he survived on loans extorted from his brothers, who were willing to support him as long as they didn’t have to see or talk to his wife Myrtle, an Australian demimondaine whose fabulist tendencies matched his own. They were living in cheap London hotels and calling themselves Baron and Baroness de Pellepoix — a completely fictional title — when their daughter Anne was born in 1930. The baby was promptly handed over to an English nurse, Elsie Lightfoot, who was effectively her mother for the rest of her childhood, with only occasional and grudging financial help from Louis and Myrtle. Being abandoned by parents such as Anne’s might have been a stroke of good luck, but it left a legacy of bitterness that not even her psychiatric training enabled her to overcome.

In 1933, destitute and disgraced, Darquier went back to Paris to live with and on his brother Jean. He was returning to a France in the throes of a quiet civil war, with quasi-fascists, extreme nationalists, ultra-Catholic royalists, and anti-Semites striving to bring down the Third Republic. Like its German counterpart, the French far right dealt in violence and hatred, and it had a particular need for shameless, brutal men to do the work of intimidation and propaganda. This was Darquier’s chance, and he seized it, insinuating himself into the world of quasi-fascist leagues like Action Française. His name was made on February 6, 1934, when a massive crowd of right-wing rioters attempted to invade the Chamber of Deputies in Paris. He had the good fortune to be shot in the leg by police, instantly becoming a nationalist hero. “It’s like having a winning ticket in the lottery,” he said frankly.

Darquier parlayed this notoriety into a seat on the Paris City Council, a leading role in a league of “veterans” of February 6, and the editorship of L’Antijuif, a newspaper whose mission was “to liberate France from Jewish tyranny.” Darquier took to Jew-hatred like a pig to slop: Never having expressed interest in the subject before, he now foamed at the mouth with blood libels taken from the Protocols of the Elders of Zion. He was soon receiving subsidies from the Nazi government (though he took pains to deny this), and after the fall of France, he was specially released from a German prisoner-of-war camp so that he could return to Paris and resume his useful work.

Darquier’s apotheosis came in June 1942 when, at German insistence, he was named head of Vichy’s Commissariat Général aux Questions Juives, the Commissiariat for Jewish Affairs. He was chosen for the post, over the objections of the French, precisely because the Nazis knew him to be a nullity who could be manipulated into anything, so long as he had the chance to enrich himself with bribes and plunder. Ms. Callil recognizes the grim comedy of Darquier’s wartime career: As his colleagues and subordinates arranged to strip French Jews of citizenship, steal their property, and send them to the gas chambers, Darquier busied himself with haranguing his cronies at bars and nightclubs. But soon even the Germans had had enough. “This bon vivant,” reads one German memo, “loses all interest in work when he finds himself in such a well-paid position … the failure of Darquier in all areas is striking.” Yet in the chaos and backbiting of Vichy, Darquier held onto his job until shortly before the Libération.

If Darquier’s incompetence had helped to save lives, even inadvertently, perhaps he would be due some credit. In fact, it simply made him the perfect fall guy, the one whose name was on the orders other men drew up and executed. And his hysterical speeches and editorials helped to create the climate in which the French Holocaust could take place. He amply deserved the death sentence that was passed on him in absentia after the war. Like so many war criminals, however, he escaped justice, and died in his bed in Spain in 1980. In a crowning irony, he survived the daughter who devoted her short life to helping people overcome their familial wounds, and ended up inheriting Anne’s estate. By telling his story so unsparingly in “Bad Faith,” Ms. Callil helps to right this historical wrong, and reminds us along the way that it does not take a great man to do a great evil.