Florence Woerth once worked for the company managing the family wealth of Liliane Bettencourt, L'Oreal heiress and France's richest woman, at a time when Woerth was both budget minister and Sarkozy's chief party fundraiser.
The government has been hit by allegations that Woerth had a conflict of interest as the minister in charge of fighting tax evasion at a time when his wife was helping manage Bettencourt's fortune and he was seeking donations.
A former Bettencourt accountant has alleged that Woerth received 150,000 euros ($A218,860) in cash from the heiress during Sarkozy's 2007 election campaign, a charge he firmly denies.
Leaked recordings of private conversations between Bettencourt and Florence Woerth's boss at the wealth management firm Clymene suggest the 87-year-old heiress was seeking to avoid tax and saw Woerth as a possible ally.
Florence Woerth's lawyer, Antoine Beauquier, confirmed he had accompanied his client to a police station in Paris for questioning on Wednesday, and said she was treated as a witness, not a suspect, and was neither detained nor charged.
"I'm pleased that Mrs Woerth can at last put her side of the story after she has been victim of so many stories in recent weeks," he said.
Sarkozy's cabinet was to meet later on Wednesday and was expected to give permission for their colleague Woerth to be questioned by prosecutors looking into the various scandals surrounding Bettencourt's vast fortune.