Blanc, who took over as coach from Raymond Domenech last month, named 13 newcomers in his first squad which did not include the 23 World Cup players suspended for one match by the France Football Federation following the team's boycott of a training session and first-round exit at the tournament.
Blanc called up Benzema against the wishes of sports minuster Roselyne Bachelot, who said the striker and World Cup player Franck Ribery, also under investigation, should not represent France.
"My answer is in the squad list and it's a clear and precise answer," Blanc told a news conference on Thursday.
"Karim's private life is none of my business. My job is to take decisions that regard sport. I think Karim has the qualities to enter the core of France team," he added.
Benzema has denied any wrongdoing and Ribery's lawyer has said the Bayern Munich player did not know the girl at the centre of the probe was under 18 at the time.
Blanc has still to chose a captain for the match in Oslo on August 11.
"There are a lot players without international experience in the squad and that will reduce my choice. I want to take time to look for someone who has enough character and above all the spirit and the mentality to assume the responsability," he said.
Midfielder Lassana Diarra and Benzema are the most capped players in the squad, both with 27 to their name.
The core of the squad comes from the generation who won the under-17 European championship in 2004 and includes several players from the victorious team - Samir Nasri, Benzema, Jeremy Menez (AS Roma) and Hatem Ben Arfa (Marseille).
"Even I had been in a position to select the 23 (World Cup players), I think some of the players I named today would have been on the list," Blanc said.
"There are a lot of players who will celebrate their first cap. I think it's a good thing and I hope they will take it with a lot joy, a lot of pride and a lot of motivation."
However, Blanc added a lot of things could change before he decides on a squad for France's first Euro 2012 qualifier against Belarus on September 3.
"Pending the result of the inquiry ordered by the French Federation on the events in South Africa, I have no information about the players who will be available," he said.
Squad:
Goalkeepers: Nicolas Douchez, Stephane Ruffier
Defence: Aly Cissokho, Mathieu Debuchy, Rod Fanni, Philippe Mexes, Adil Rami, Mamadou Sakho, Benoit Tremoulinas.
Midfielders: Yohan Cabaye, Lassama Diara, Blaise Matuidi, Yann Mvila, Samir Nasri, Charles N'Zogbia, Moussa Sissoko.
Forwards: Hatem Ben Arfa, Karim Benzema, Jimmy Briand, Guillaume Hoarau, Jeremy Menez, Loic Remy.
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