Inter’s win was coupled with second-placed AS Roma's 2-1 loss at Atalanta. The Milanese giants now have an unassailable 16-point lead with five games left to play.

Marco Materazzi was the hero as he scored the double that helped Inter Milan retain the Scudetto title they were awarded last season after Juventus were dethroned for their role in a match-fixing scandal.

Materazzi opened the score in the 18th minute when he pounced on the rebound after Siena keeper Alex Manninger fumbled Maicon’s header.

Three minutes later Paolo Negro put Siena at level.

Materazzi regained the lead on the hour when he slotted home from the penalty spot after Julio Cruz was pinned in the area.

Elsewhere, Roma slipped to a 2-1 defeat against Atalanta.

Cristiano Doni and Ricardo Zampagna scored for the home side in the first-half while Simone Perrotta scored Roma’s consolation goal in the 65th minute.

In other matches, Lazio slipped to fourth place after losing to Fiorentina 1-0, Chievo edged past Livorno with a 2-1 win, Udinese held Reggina to a 1-1 draw while Empoli and Torino settled for a goalless stalemate.