P Diddy�s split from long-suffering girlfriend, Kim Porter, could cost him $1.2 million a year in child support.

The hard-partying rapper already pays the mother of one of his many children $30,000 a month in child support for their son, Justin.

And since Kim has three children with him - Christian, 10, and 7-month-old twins D'Lila Star and Jesse James � Page Six are calculating that this could cost Diddy � aka Sean Combs - as much as $1 million.

"With Misa Hylton-Brim receiving approximately $30,000 a month, there is no reason that Ms. Porter shouldn't be able to get close to $100,000 or more per month in child support," celebrity divorce lawyer Raoul Felder told Page Six.

"That amount accounts for Porter having three children with Combs and inflation in the years since Misa received the ruling in her case."

Friends say that the rapper has left himself open to a big pay out because he had no pre-or post-nuptial agreement with Kim.