Guess Inc. says its co-founder Paul Marciano is stepping down after the completion of a company-commissioned investigation into allegations of sexual harassment and assault.

The Los Angeles-based fashion company announced in a filing Tuesday with the US Securities and Exchange Commission Marciano would resign immediately as executive chairman of the Guess board and his brother and co-founder Maurice Marciano would take over.

Paul Marciano, who has denied the allegations, will remain a board member and stay on as chief creative officer through January.

The filing says allegations against Paul Marciano included inappropriate comments and texts and unwanted kissing and groping.

It said many of the allegations could not be corroborated but others were credible.

The company says it has settled lawsuits with five of Paul Marciano's accusers for a total of $US500,000 ($A660,000).