Swiss police have searched the home of Bruno Doessekker, the author of a contested award-winning account of childhood survival in Nazi concentration camps.

Deception charges were filed last November by Manfred Kuhn, a Zürich-based lawyer, who claims that Doessekker defrauded him and about 12,000 other readers of the cost of the book.

A district prosecutor, Lucienne Fauquex, who is examining the case, confirmed the search at Doessekker's Swiss flat, and said the investigation would take several months to complete.

Upon publication in 1995, the alleged autobiography, Bruchstüke (Fragments of a Childhood, 1939-1948), was hailed as a moving account of a three- to four-year-old Latvian-Jewish boy's life in concentration camps in Poland.

Copies of the book were withdrawn by Suhrkamp-Verlag, the German publisher, during last year's Frankfurt book fair.

After the work was first challenged by a Swiss journalist, Daniel Ganzfried, in 1998, research commissioned by Suhrkamp and Does-sekker's agent appeared to back up the allegations that the author presented a fictitious childhood as an orphan, and was neither Latvian nor Jewish.

For more than a year Ganzfried cast doubt on the account, starting a high-profile debate in the interna tional press. The book received Jewish literary awards in the US and France. Doessekker made speaking tours in the US as a guest of the Holocaust memorial museum.

Writing as Binjamin Wilkomirski, which he claimed to be his original identity, Doessekker described the horrors of Auschwitz and Majdanek death camps and how he saw his father beaten to death.

The bulk of the evidence presented by his critics indicates that Doessekker was indeed adopted, but was born in Biel, Switzerland, on 12 February 1941 as Bruno Grosjean to a single mother, a Christian. He was brought up during the Second World War by his adoptive family, the Doessekkers, near Zürich.

The publisher's subsequent research is said to have shown that Bruno did not leave neutral Switzerland during the war.

The Zürich prosecutor has questioned Doessekker, but declined to give further details on the case.