Two forestry companies colluded for more than a decade to control the prices of toilet paper and other products, according to Chile's competitive practices regulator.

Economy Minister Luis Felipe Cespedes said on Thursday that the collusion between the market's biggest players was outrageous and affected the poorest Chileans the most.

Chilean President Michelle Bachelet called the alleged collusion by companies that control 90 percent of the toilet-paper market "extremely serious".

The regulator, the Fiscalia Nacional Economica, said on Wednesday that an antitrust court accepted its filing accusing the companies of colluding to control prices of toilet paper, napkins, absorbent towels and other products from 2000 to 2011.

"It's one of the biggest collusion cases ever uncovered in the country," the FNE said.

CMPC Tissue SA, however, will not be fined because the company acknowledged the anticompetitive conduct earlier this year. The regulation agency asked the court to sanction SCA Chile SA, but the company is expected to get a reduced fine because it also acknowledged wrongdoing.

CMPC Chile said that it had fired the general manager of its tissue division and other company executives involved in the collusion scheme.

"The fact that some of our executives carried out acts that go against free competition is illegal and also deeply affects our way of acting as a company, our corporate policies and our organizational culture," CMPC said in a statement.

Swedish-owned SCA could not be reached for comment.

The FNE said the collusion apparently began when the then-manager of CMPC began meeting with the owner of PISA - a company that SCA bought in 2012 - at a golf club in the Chilean capital.