Oliver Morice, who represents victims of a 2002 Karachi bombing that killed 11 French naval engineers, said the probe is finally getting to senior politicians, France 24 reported Wednesday.
The bomb attack was believed to be revenge for a French government decision to halt bribes to Pakistani officials.
The latest French politician to be detained for questioning is Renaud Donnedieu de Vabres who served as an adviser to then-Defense Minister Francois Leotard in 1994. He was France's minister of culture from 2004 to 2007.
That was the year a deal was finalized for the sales of French-made submarines to Pakistan.
De Vabres is suspected of complicity in arranging illegal bribes that helped finalize the sales, as well as kickbacks in the form of commission payments that allegedly found their way back to senior French politicians, the report said.
Some of the kickback cash allegedly was used to fund then-Prime Minister Edouard Balladur's failed 1995 presidential campaign, the report said.
"Renaud de Vabres is the first of the politicians to feel the long arm of the law," Morice said. "No doubt Francois Leotard and Edouard Balladur will be next."