French Interior Minister Nicolas Sarkozy has ordered an investigation into claims that police tortured terror suspects in 1995.
Five former police officers gave accounts of abuse in the book
The allegations have been published in a book which includes accounts by five former police officers who say suspects were beaten and given electric shocks.
The former director of police at the time of the alleged abuse said he was shocked and denied the use of torture.
France is to come under fire over its prison system in a report this week.
The human rights watchdog, the Council of Europe, says prisons are overcrowded and police operate with a sense of impunity, according to excerpts from a report due out on Wednesday.
The allegations made in the book Place Beauvau, named after the interior ministry's headquarters, relate to police investigating a wave of bombings in France by radical Islamists in the 1990s.
The former police officers, who are not named in the book, say they took part in some of the abuse of terror suspects in custody in Paris and the south-eastern city of Lyon.
One suspect is said to have been dangled out of a sixth-floor window, according to the AFP news agency.
Mr Sarkozy told French RMC radio: "Either the facts are proved and, in that case, there will be disciplinary action.
Eight died in the Paris Saint Michel Metro bombing in 1995
"Or these are lies, and in that case I reserve the right to protect the honour of men whose work allowed lives to be saved."
He said he launched an inquiry as soon as he heard the claims and promised the findings would be published.
"I am astonished that incidents this serious were never denounced, considering the number of people who were present at the interrogations," he said.
He called on those who were in government at the time to comment.
The head of the national police force at the time, Claude Gueant, said he was astonished by the claims in the book, written by three journalists from the news magazine Le Point.
Among the worst attacks during the bombing campaign by Algeria's outlawed Armed Islamic Group (GIA) was the attack on the Saint Michel metro station on 25 July 1995, in which eight people were killed and 87 injured.