Italy's caretaker prime minister was assembling a cabinet lineup on Tuesday despite almost certain rejection by populist parties whose bid for power collapsed at the weekend.
Carlo Cottarelli, a former IMF economist known as "Mr Scissors", was tasked with naming a technocrat government on Monday after President Sergio Mattarella blocked a cabinet proposed by the far-right League and anti-establishment Five Star Movement (M5S).
Cottarelli said Italy would face new elections "after August" if parliament did not endorse his team, a near certainty given that Five Star and the League together hold a majority.
Elections could benefit Salvini, however, as recent polling by IndexResearch put the League at 22 percent, five points up from its vote share in the March 4 ballot.
However, Di Maio said that Mattarella, a former constitutional court judge, had "gone beyond his legal prerogatives".
He said an impeachment trial for Mattarella, 76, would be "almost a certainty".