Brazilian police are investigating allegations that ex-President Fernando Henrique Cardoso asked a private company to pay his former lover abroad.
Former TV journalist Mirian Dutra says Mr Cardoso arranged the $3,000 monthly payments through the firm, Brasif.
The transfers began in 2002 - a year before Mr Cardoso left office.
Mr Cardoso denies the allegations. Brasif also says Ms Dutra was paid for work she did for them and the former leader had nothing to do with it.
Ms Dutra worked as a reporter for Brazil's Globo TV for 35 years, losing her job last December.
"I don't want to take this to my grave," she said said in interview with Folha de Sao Paulo newspaper.
Mr Cardoso has acknowledged the six-year-long affair with her, which came to an end before he became president of Brazil.
Ms Dutra said their relationship ended when she refused Mr Cardoso's suggestion that she should have an abortion, which is illegal in Brazil.
After her son Tomas was born, she asked Globo TV to transfer her to Lisbon. After a few years, they moved to Spain.
Mr Cardoso supported Ms Dutra and her son abroad, she said.
But between December 2002 and December 2006 the money came from Brasif, a company that had a licence to operate duty-free shops at a number of Brazilian airports, she said.
She said she signed a fictitious contract with the company but never worked for them.
"He sent me money through this company. I have evidence," she said.
"It was all arranged by my sister's husband, Fernando Lemos, who was the top lobbyist in Brasilia at the time," added Ms Dutra.
Mr Cardoso has admitted sending money to Ms Dutra and Tomas abroad, but denies using Brasif or any other company for that purpose.
Brasif said in a statement that it hired Ms Dutra to do research on duty-free shops in European airports.
It confirmed the payments but said the former president had no involvement in their decision to hire her.
Mr Cardoso never transferred any money to the company, Brasif added.
The former president recognised the paternity of Tomas and bought him a flat in Barcelona. He says a 2011 DNA tests proved that Tomas was not his son. Ms Dutra questions the validity and accuracy of the test.