9:26 AM PT -- Naomi Campbell was not late to Tuesday evening's Harlem's Fashion Row Fashion Show and Style Awards, despite Anna Wintour's dig ... TMZ has learned.

Sources close to Naomi tell TMZ ... the supermodel arrived at the time she was instructed to by the event's producers. We're told it was Anna who moved up the presentation slot ... since the Vogue editor wanted to make her way to the US Open.

AW did end up at the tennis tournament ... and was photographed having a nice time with the other attendees.

Naomi didn't know why Anna left early ... but we're told the model clocked the fashion guru's exit and was disappointed by it -- prompting her to make her own shady remark onstage.

NC wasn't just pissed about Anna snubbing her ... she was also upset about the designers who were putting on a show that night and wouldn't get to impress AW.

Naomi Campbell and Anna Wintour got into a catfight of sorts during an NYC fashion show ... with the two legends dissing each other onstage in front of a packed audience.

It was the supermodel versus the Vogue editor at Tuesday night's Harlem's Fashion Row Fashion Show and Style Awards -- and it all started with Anna stepping up to the podium onstage to needle Naomi for being tardy to the party.

Anna told the crowd, “I am a very punctual person, and I have the honor of presenting tonight to someone who is often late.” Of course, Anna was referring to Naomi ... and Wintour got so fed up with the lack of punctuality she eventually left.

Her exit prompted Samira Nasr -- Harper's Bazaar editor-in-chief -- to present the Fashion Icon Award to Naomi, who took to the stage to accept the statue.

Naomi first admitted she's always late ... but said things always work out the way they're supposed to.

Then Naomi took a dig at Anna -- explaining she preferred having Nasr present her with the award instead of Wintour.

Naomi said ... “It wasn’t my choice to have the other lady [Wintour]. I’d much rather have this” -- meaning Nasr.

Many people in the room seemed stunned and let out audible gasps.

For now, it seems Anna and Naomi won't be on each other's Christmas lists.