Orlando Figes has written many successful books
A leading historian has admitted writing anonymous online reviews condemning his rivals' work.
Orlando Figes, a professor at London's Birkbeck College and the author of many books on Russian history, wrote the negative reviews on the Amazon website.
His admission follows a row between top UK historians over the string of reviews that praised Figes while criticising other authors.
In a statement, Figes - now on sick leave - "apologised wholeheartedly".
Robert Service, a respected historian of the Soviet Union and the subject of one of Figes' anonymous reviews, wrote in the Guardian newspaper that the "secretive rubbishing of my work... [was] disgraceful."
According to a detailed account of the row in the Times Literary Supplement (TLS), the controversy began when Rachel Polonsky - a writer and Russian expert - discovered a hostile review of her recently-published book on Amazon.
The comments posted online said her work was "hard to follow". Others described a book by Robert Service as "awful".
Meanwhile the reviewer who used the online moniker, "orlando-birkbeck", had reportedly praised a book by Figes as "fascinating".
Figes said in a statement: "I take full responsibility for posting anonymous reviews on Amazon.
"I have made some foolish errors and apologise wholeheartedly to all concerned. In particular, I am sorry for the distress I have caused to Rachel Polonsky and Robert Service."
Figes, 50, is a prizewinning author known for his works about Russia, including Natasha's Dance: A Cultural History of Russia and The Whisperers: Private Life in Stalin's Russia.
The true identity of the reviewer came to light after Polonsky discovered that the reviewer shared the same home address as Figes, said the TLS, which went public with the row last week.
The TLS said that initially, when confronted by the allegations of his involvement, Figes' instructed his lawyer to threaten legal action.
Subsequently, it said, Figes stated that his wife, a leading human rights lawyer, had written the comments.
On Friday, the historian issued a statement apologising to those he had written about, his lawyer, and his wife.
"I panicked when confronted with an email sent to academics and the press and instructed my lawyer without thinking this through rationally.
"This escalated the situation and brought more pressure on myself by prompting a legal response.
"My wife loyally tried to save me and protect our family at a moment of intense stress when she was worried for my health, and I owe her an unreserved apology."
Figes said he was "ashamed" of his behaviour and did not entirely understand why he acted as he did.
He said: "It was stupid - some of the reviews I now see were small-minded and ungenerous but they were not intended to harm.
"This crisis has exposed some health problems, though I offer that more as explanation than excuse.
"I need some time now to reflect on what I have done and the consequences of my actions with medical help."