Nicolas Sarkozy said on RMC radio on Monday: "As soon as the facts were brought to my attention, I launched an inquiry by the National Police General Inspectorate. This inquiry is on-going, I will publish all elements of this inquiry.
"Either the facts are proved and, in that case, there will be disciplinary action. 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.
Sarkozy ordered the inquiry after five former police officers confessed in a new book to taking part in, or witnessing, beatings and torture of suspects in 1995.
The alleged abuse was carried out by officers investigating attacks by Algeria's Armed Islamic Group (GIA) which killed 10 people and wounded about 200 others between July and November 1995.
"Either the facts are proved and, in that case, there will be disciplinary action. 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"
French interior minister
"We are 11 years after the facts, nobody has ever heard talk of this before. The witness accounts are sometimes anonymous," Sarkozy added.
The authors quote former officers as saying the suspects were tortured with electricity, beaten, and deprived of water and food for several days.
Some of those quoted, who are not named, said they took part in the torture, which is said to have taken place in Paris and the southeastern city of Lyon.
In the most serious incident during the 1995 campaign of attacks, 8 people died and 150 were wounded when a homemade device filled with nails and bolts exploded in the busy St Michel suburban railway station in central Paris.