Argentine Treasury Secretary Nicolas Duchovny resigned and said in a letter seen by Reuters that he felt the government needed a "major renewal" in its economic team amid a crisis that saw the peso plunge last week.
In a letter to Argentine President Mauricio Macri, Duchovny said he had given "all" his energy to his work and contributed to reducing the large deficit and reducing public spending.
"We have also made mistakes, no doubt, and we have never hesitated to admit it and have made every effort to correct it."
The source told Reuters that Macri appointed Hernan Laconza, the current economy minister for the province of Buenos Aires, to succeed Dokhovny.
The Argentine peso has fallen sharply for most of the past week, after Sunday's primaries produced a shocking result, with center-left candidate Alberto Fernandez downing center-right Macri in what was widely seen as a referendum on the government's bid for an IMF loan. And conditional austerity measures to lend.
In a fresh blow to Macri, Fitch and Standard & Poor's on Friday downgraded their sovereign debt rating, raising the specter of Argentina's default as the October elections approach.
Laconza previously served as general manager of the Central Bank of Argentina.