In November, judges were authorised to probe corruption charges against three heads of state: Congo-Brazzaville's President Denis Sassou Nguesso, Equatorial Guinea's Teodoro Obiang Nguema, and Omar Bongo, the late president of Gabon, who died in 2009.
Anti-corruption campaign group Transparency International (TI) had brought civil charges in 2008 accusing them and their relatives of embezzling state funds to buy cars and apartments in France worth tens of millions of euros.
TI brought the charges to bypass French state prosecutors, who are under government authority and had dropped previous cases brought against the leaders since 2007 – amid allegations of collusion between Paris and leaders of its former African colonies.
The Le Monde newspaper reported on Thursday however that extravagant purchases had continued since that suit was lodged, with the leaders and their families buying Bentleys, Ferraris, Porsches and other cars worth millions.
The lawyer representing TI, William Bourdon, said investigating judges had asked for authorisation to probe these most recent alleged purchases in addition to the earlier ones, but that state prosecutors had refused it.
"It is a staggering decision which works against the efficiency of the investigation and is in line with the prosecutors' obstructive approach since 2007," Bourdon told AFP.