Milito scored a tap-in and two penalties while opposite number Zlatan Ibrahimovic hit a spot kick and a superb flick-finish.
Maicon added a spectacular fourth to put the result beyond doubt, ending the Rossoneri’s hopes of defending the title with one match left.
A hugely entertaining clash at the Giuseppe Meazza / San Siro had it all - goals, controversial penalties (and non-penalties) and a parallel encounter in Trieste as Juve beat Cagliari 2-0 to seal their first title win since Calciopoli.
A feisty and entertaining first half finished level in some controversy.
Inter started by far the better, relaxed and vibrant as the Rossoneri struggled to hit their rhythm.
The first good chance fell to Milan, carved out by a wonderful dipping cross from Robinho that landed perfectly for an Ibrahimovic tap-in, but he somehow blazed over from six yards.
Soon afterwards it was 1-0 to Inter as, from a Wesley Sneijder free-kick, an unmarked Walter Samuel knocked the ball across goal for a similarly free Milito, who tapped home from close range.
With Juventus leading at Cagliari thanks to Mirko Vucinic, Milan had to try and win the match let alone equalise, but appeared shell-shocked as Inter almost snatched a second.
Lucio had the ball in the back of the net after Sneijder’s free-kick was parried by Christian Abbiati, but the Brazil defender was correctly adjudged offside; Esteban Cambiasso was then denied by Abbiati’s sensational stop, with the Milan keeper picking up a game-ending injury in the process; seconds later, Sneijder found the side netting after he appeared alone on the left.
That last escape appeared to spark Milan into action, and they were the better side in the closing stages as Julio Cesar denied Ibrahimovic with a fine save.
Then came a moment of huge controversy: Kevin-Prince Boateng’s heavy touch took him and ball into the box but too close to Cesar, who clearly palmed the ball away from the Ghana midfielder.
But referee Nicola Rizzolo pointed to the spot, all the more shocking given the lack of appeal from Boateng, who knew he had not been fouled.
After some gamesmanship between the Inter keeper and his former team-mate, Ibrahimovic rifled a low finish inside the left-hand post.
Juve were winning the title as it stood, the unbeaten Bianconeri with a superior head-to-head courtesy of their 2-0 win over Milan in Turin earlier in the season.
But 34 seconds into the second half a moment of genius from Ibrahimovic saw Milan edge ahead and keep their title hopes alive.
Antonio Nocerino’s low ball across the face of goal was dummied by Boateng, with Ibrahimovic flicking the ball around Lucio, spinning clear and chipping the onrushing Cesar in style.
It was an outrageous effort - almost as audacious as Sneijder’s 50-yard volley that almost caught out a backtracking Marco Amelia, who managed to palm it away.
In addition to their own European ambitious, Inter wanted to end Milan’s title hopes in front of their own fans and they were level soon afterwards when the referee evened out the penalty calls, although the Nerazzurri’s first was clear-cut as Ignazio Abate hauled down Milito in the box.
The Argentine dusted himself off to rifle the spot-kick into the top left and it was well and truly game on, with both sides desperate for victory.
Milan almost went back in front immediately when Sulley Muntari - on loan from Inter - cold only watch as the ball bounced wide of an empty net after Ibrahimovic’s header cannoned off the Ghanaian.
Robinho forced a good stop from Cesar as the match seemed to swing back in Milan’s favour, with Cesar also denying Abate after the full-back cut inside from the right.
Then news filtered through of a comical second for Juve, Michele Canini with a bizarre own-goal, and it seemed to knock the stuffing out of Milan.
But the goal that edged Inter ahead on the night was almost as debatable as Milan’s earlier: substitute Giampaolo Pazzini flicked a header in the box, Alessandro Nesta less than a yard away as the ball spun up into his arm.
It was clearly unintentional, although the referee would argue that his arm was raised. Possibly mindful of his earlier error, Rizzoli pointed to the spot, levelling the dodgy calls for the time being.
Miltio smashed it into the top right, completing his hat-trick to spark wild celebrations on the bench and stands - mirrored in Trieste, where Cagliari and Juve’s game was being played due to a stadium dispute in Sardinia.
There was a final moment of controversy when an Ibrahimovic cross appeared to strike Cambiasso on the arm, more of a penalty than the previously-awarded effort, but the ‘visiting’ side’s appeals were waved away.
With nine minutes left Milan were finished, the latter stages played out as an exhibition match for Inter’s fans - although that was inspired by Maicon’s wonder-goal, the Brazilian full-back hitting a dipping, swerving strike from the right wing into the top left.
He was assisted by the tireless Javier Zanetti, who at one point ran the full length of the pitch to win a corner, while Lucio went close with a deflected free-kick before Cambiasso fired wide deep into injury time.
Around four-and-a half-additional minutes were played but Inter were already celebrating, sticking the knife into their rivals while putting themselves sixth as the chase for European places goes to the wire.
Milan, meanwhile, must lick their wounds ahead of next season, with a rebuilding project set to focus on a creaking defence that has conceded 13 more goals than Juve this campaign.