A dozen anti-graft campaigners have filed a complaint against logistics group Bollore and its former CEO with the French financial prosecutor, accusing them of using connections and influence-peddling to secure lucrative African port concessions.

The complaint is the first step towards a possible criminal case in France.

The campaigners' complaint, which demands restitution, alleges that the Bollore Group and Vincent Bollore, used connections with leaders across West Africa over several decades to win contracts and build up an expansive business network.

These included port concessions in Togo, Ghana, Guinea, Cameroon and Ivory Coast, secured by way of "corruption, favouritism and influence peddling," according to the complaint filed late on Tuesday, which Reuters reviewed.

Those contracts earned billions of euros for the group that should be returned to local populations, the complaint says.

A representative for the Bollore Group and Vincent Bollore did not respond to a Reuters' request for comment on the allegations. A lawyer for the Bollore Group declined to comment.

The financial prosecutors (PNF) will now decide if there are sufficient grounds to launch an investigation. If rejected, the plaintiffs are able to file a second complaint that would force the opening of a preliminary probe.

The PNF did not respond to a request for comment.

A dozen associations, including Restitution Afrique (RAF), which is funded by Congolese whistleblower Jean-Jacques Lumumba, and Transparency International's branches in Cameroon and Ghana, are listed as plaintiffs in the complaint.

It says that revenue from Bollore's Africa concessions helped to underpin the 5.7 billion-euro ($6.2 billion) price tag on Bollore Africa Logistics' 2022 sale to French shipping group CMA GGM.

The complaint demands that all or part of money earned from the sale be returned to local populations under a French law passed in 2021.

The governments of Togo, Cameroon, Ghana and Ivory Coast did not immediately respond to a request for comment on the complaint's main arguments. The government of Guinea could not be reached for comment.

RAF lawyer Antoine Vey told Reuters his clients expected an investigation into the group's "money flows".