Mexican President Vicente Fox says his wife, Marta Sahagun, has no plans to run for the presidency when he ends his term in office in 2006.
The first lady heads a highly visible charity called Let's Go Mexico
Mr Fox was responding to fierce criticism of his wife's widely reported ambitions to succeed him.
Mr Fox's chief aide quit this week, saying the first lady's political influence was increasing.
Ms Sahagun, who has neither confirmed nor denied the reports, is an active campaigner and runs her own charity.
Mr Fox, constitutionally barred from seeking a second term, said he and his wife would return to his family's ranch when he leaves the presidential post in 2006.
"Marta and I have very concrete plans," Mr Fox told reporters.
"We know when it's time for us to leave Los Pinos [the presidential mansion] and we know what our next project will be; we are very clear on that. We won't be seen in politics."
Mr Fox's comments came after his chief of staff, Alfonso Durazo, resigned on Monday, leaving a stinging letter which cited in particular the first lady's presidential ambitions.
"The country has certainly advanced politically, enough
that it is ready for a woman to reach the presidency of the republic," Mr Durazo said in his 19-page letter.
The couple married a year after Mr Fox came to office
"Nonetheless, it is not prepared to have the president leave the presidency to his wife."
Mr Durazo slammed Mr Fox for repeating the vices of the old ruling party, the Institutional Revolutionary Party, the PRI, which had a tradition of determining the presidential succession.
Marta Sahagun has been widely criticised by some sectors of the Mexican media, which have accused her of manipulating her husband and being the real power behind the throne.
Her activism, especially with her charitable foundation Vamos Mexico, has also angered some within Mr Fox's own party, who complain she has an unfair advantage.
Ms Sahagun is Mr Fox's former press secretary. The couple, both divorced, fell in love during his presidential campaign in 2000 and married a year later.