Coming into the game off the back of two straight draws and only two wins in their previous six league games, Milan were starting to come under pressure from the chasing pack, notably a revitalised Inter Milan and surprise package Napoli yesterday.
And second-placed Napoli remained hot on their heels three points back as league top scorer Edinson Cavani bagged a brace to down Roma 2-0.
Milan coach Massimiliano Allegri claimed, though, that the rossoneri have never been under pressure.
"Obviously (the last two draws) added weight to the voices talking about a crisis and gave hope to those chasing us," he said.
"But there was never a critical moment because in both those games the only thing lacking was the result.
"The lads did really well." First half goals from Clarence Seedorf and Antonio Cassano, his first for the club, put this game to bed before the break.
Substitute Robinho then scored a second half brace to emphasise Milan's superiority.
"We played well and played a great game and I'm also happy because my goals helped us win," Robinho told SkySport before looking ahead to Tuesday's Champions League clash against Tottenham.
"They're a great team but we want to win everything, we're not looking at other teams.
"We're only thinking about playing well and I think we can win the title."
Milan were on the charge from the off with Seedorf forcing visiting goalkeeper Antonio Mirante into a diving save from a rasping drive in the first minute.
Parma could not handle Milan's attacking flair and on eight minutes Zlatan Ibrahimovic played Seedorf in behind the defence to round Mirante and slot home on the slide.
The second came on 17 minutes after a delightful exchange with Cassano coming in from the left, playing the ball inside to Gennaro Gattuso and taking his dinked reverse pass over the Parma defence to slot slow into the corner on the half volley.
Milan were rampant and it could have been more just after the half hour mark.
Ibrahimovic nodded the ball back down for Cassano but his shot was tipped away for a corner.
Cassano then chipped the ball over the defence for Ibrahimovic to take down on his chest and volley goalwards but Mirante came to his side's rescue.
Parma offered almost nothing in attack with only a misdirected header from Milan centre-back Thiago Silva troubling his own goalkeeper Christian Abbiati just before half-time.
Parma were a much improved outfit in the second period with Sebastian Giovinco's shot being charged down by the returning Alessandro Nesta.
Blerim Dzemaili then had a fierce shot from distance parried by a diving Abbiati before Massimo Pacci failed to make contact from eight yards with a goal begging.
But just as the visitors were enjoying their best period of the game, Milan made it four.
Robinho arrived unmarked on 61 minutes to finish from 15 yards after Cassano tried to tee up Ibrahimovic.
The Brazilian then fluffed his lines when running on to a cross from Ibrahimovic but he made no mistake moments later as Cassano ran at the defence and slippped him in for another precise and clinical finish.
Napoli all but mathematically ended Roma's title chances by claiming their first win away to the giallorossi in 17 years.
Cavani opened the scoring on 49 minutes from the penalty spot after Juan had clipped Marek Hamsik's heel in the area.
And the Uruguayan finished things off seven minutes from time as he stabbed home Paolo Cannavaro's cross from six yards.
Roma now trail Milan by 13 points, although with a game in hand.