Antonio Conte's side had drawn its three previous league outings and, with leader Juventus defeating Fiorentina 3-0 earlier in the day, appeared in danger of losing further ground in the title race.

However, after a scoreless first half, Lukaku's brace moved Inter back above Lazio and into second place, three points behind the reigning champion.  

January additions Christian Eriksen and Victor Moses were handed their full debuts by Conte while teenager Sebastiano Esposito filled in up front for the suspended Lautaro Martinez.

Yet the fresh faces failed to inspire, and it was Udinese who were the more threatening side in the first half. Seko Fofana fired into the side netting and Jens Stryger Larsen saw an on-target strike blocked by Ashley Young.

Lukaku had been on the periphery of proceedings before converting his first attempt of the game, his low, left-footed effort in the 64th minute going through the legs of Bram Nuytinck to beat Juan Musso.

The Belgian's second arrived from the penalty spot seven minutes later, Musso having been spectacularly up-ending Alexis Sanchez as the substitute attempted to skip beyond the advancing goalkeeper.

Kevin Lasagna twice dragged efforts wide in the closing stages as Udinese drew a blank, the hosts managing just one shot on target as they allowed Inter goalkeeper Daniele Padelli a comfortable outing while standing in for the injured Samir Handanovic.