Juventus ended 2013 five points clear at the top of Serie A after a 4-1 victory at Atalanta stretched their winning league run to nine games on Sunday.
AS Roma remained their closest pursuers following a 4-0 crushing of bottom club Catania with two goals from defender Mehdi Benatia.
A delicate backheel from Rodrigo Palacio's earned Inter the spoils four minutes from the end of the Milan derby and moved them up to fifth on 31 points.
Milan have only won one league game in two months and are languishing in 13th place on 19 points, only five away from the relegation zone, after a poor performance in which Sulley Muntari was sent off in stoppage following a scuffle.
Carlos Tevez's 11th league goal of the season after six minutes and strikes from Paul Pogba, Fernando Llorente and Arturo Vidal tightened Juve's grip on top spot with 46 points from 17 games.
Roma, still unbeaten, have 41 points after they dispatched Sicilians Catania with goals also coming from Mattia Destro, his third in as many games, and Gervinho.
"The first half wasn't very good but the second half was stellar. The second half is how I always want to see Roma," Roma coach Rudi Garcia told reporters.
"Fourty-one points after 17 games is extraordinary, any other year we would be top. But this year there is a Juve that wins every game."
Giuseppe Rossi's 14th league goal of the season helped Fiorentina scrape a nervy 1-0 win at lowly Sassuolo that lifted them to 33 points in fourth place, three points behind Napoli.
Hellas Verona hammered struggling Lazio 4-1 through a Luca Toni brace and further goals from Romulo and Juan Iturbe and they lie sixth on 29 points.
Sampdoria continued their unbeaten run under new manager Sinisa Mihajlovic with a 1-1 draw against Parma and Torino hammered Chievo 4-1.
Juve were ahead after six minutes as Tevez collected Arturo's Vidal's misplaced pass and fired home.
Maxi Moralez struck a shock equaliser nine minutes later, drilling a low first time drive off the post and past Gianluigi Buffon, the first goal he had conceded in nine league games.
The champions remained on top, however, and Pogba put them back in front after the break, calmly slotting home after Llorente touched down Kwadwo Asamoah's cross.
Llorente removed any doubt as to the outcome when he took Giorgio Chiellini's pass with his back to goal and brilliantly worked a shooting position before firing home.
A long-range strike from Alessandro Diamanti helped struggling Bologna beat Genoa 1-0 and move out of the relegation zone, relieving the pressure on manager Stefano Pioli.
According to local media reports, Bologna chairman Albano Guaraldi wants Italy great Roberto Baggio to replace Pioli, who received a huge show of support from home fans.
Internazionale 1-0 AC Milan, Torino 4-1 Chievo, AS Roma 4-0 Catania, Atalanta 1-4 Juventus, Verona 4-1 Lazio, Sassuolo 0-1 Fiorentina, Sampdoria 1-1 Parma,Bologna 1-0 Genoa, Cagliari 1-1 Napoli, Livorno 1-2Udinese