Japanese authorities have alleged that companies rigged the bids for 26 contracts worth $3.95m.

The Japan Fair Trade Commission said on Tuesday it filed the complaint against the six firms and seven individuals after determining that the “malicious and serious case” would have a “broad impact on people’s lives”.

The six advertising firms named in the complaint are Dentsu, Hakuhodo DY Holdings, Tokyu Agency Inc, Fuji Creative Corporation, Cerespo Co and Same Two Inc.

The move comes following months of investigations by authorities into claims that companies conspired to rig bids for events in the run-up to the Olympics in violation of Japan’s antimonopoly laws.

Authorities have alleged that the bid rigging involved 26 supposedly open tenders worth 538 million Japanese yen ($3.95m).

Prosecutors earlier this month arrested a former Tokyo Olympics organising committee official and executives at Dentsu, Fuji Creative and Cerespo in connection with the case.

On Friday, Dentsu chief executive Hiroshi Igarashi admitted to prosecutors that his company had rigged bids for contracts related to the Games, Kyodo News reported, citing unnamed sources close to the matter.

Dentsu, Cerespo and Fuji Creative have already been slapped with a nine-month ban from bidding for contracts at several government ministries.

The scandal follows the arrest last year of Haruyuki Takahashi, a former Olympics board member and Dentsu executive, on suspicion of taking bribes from sponsors.

Executives from advertising firm ADK Holdings, clothing retailer Aoki Holdings and publishing company Kadokawa have also been arrested in connection with the bribery case.