Rio De Janeiro, Sep 12 (IANS): Brazilian President Dilma Rousseff has dismissed presidential rival Marina Silva's statement as "thoughtless" that ruling party had used a former director of a state-run oil giant to "steal from the company's vaults".

Silva said in an interview earlier Thursday that Rousseff's Workers' Party (PT) planted Roberto Costa, a former director of the Petrobras, in the oil giant for 12 years to "steal from the company's vaults".

Costa, arrested in a recent operation against corruption, revealed a supposed bribery scandal inside the Petrobras, involving many politicians.

At a press conference in Brasilia, Rousseff said Silva spent most of her political career in the PT, first as a city representative, then as a senator and environment minister, Xinhua reported.

"I think the candidate must stop using her personal convenience to make statements," said Rousseff about Silva.

"She was in the PT for 27 years, she got all her mandates while she was in the PT, and, out of the 12 years she mentioned, she was either in the government or the Senate for eight (years)."

"I do not believe it is possible for people to have positions which (he) does not honour," Rousseff added, saying she deeply regretted Silva's statements and considered it as "thoughtless and inconsequent".

Marina Silva left the PT in 2009 and joined the Green Party, running for presidency in 2010. She later left the Green Party and last year joined the Brazilian Socialist Party (PSB) after a failed attempt to found a party of her own.

She first served as a vice presidential candidate to Eduardo Campos, then took over the party's presidential candidacy after Campos died last month in a plane crash.