Argentina's Treasury Minister Nicolas Dujovne has resigned, saying in a letter on Saturday he believed the government needed "significant renewal" in its economic team amid a crisis which saw the peso plunge this week.

Dujovne said in a letter to Argentine President Mauricio Macri that he had given his "all" to the job, helped tame a significant deficit and trim public spending.

"We have made mistakes as well, without a doubt, we never hesitate to recognize that and did all that was possible to correct them," he added.

"I believe my resignation is in keeping with my place in a government… that listens to the people and acts accordingly," he added.

Macri has appointed Hernan Lacunza, the current economy minister for Buenos Aires province, as Dujovne's replacement, Reuters reported.

Argentina's peso was in free fall for most of this week after a shock primary election result on Sunday, when center-left Peronist candidate Alberto Fernandez trounced center-right Macri, in what was widely seen as a referendum on the government's seeking of a loan from the International Monetary Fund and austerity measures it took as a condition for the loan.

The peso depreciated 21 percent by the end of the week and on Friday, in a fresh blow to Macri, ratings agencies Fitch and S&P downgraded Argentina's sovereign debt rating, raising the specter of a default as the October election approaches.

Lacunza is the former general manager of Argentina's Central Bank and also of the Buenos Aires City Bank.