A widening rift has developed between Matthew McConaughey and his baby mama Camila Alves – and her mother is smack dab in the middle of it!

Camila’s mom Multo Abrigado is pushing her unmarried daughter – mother of Matthew’s two children – to work out a financial agreement with the big-screen hunk, sources say.

But the 40-year-old bachelor is balking, insiders say.

 "Camila’s mother is very traditional, and she’s worried that since they are not married, Matthew could leave her daughter high and dry with two kids if he falls out of love with her," a source divulged.

"She’s been telling Cam that she needs to force Matthew into a financial agreement, but when Cam brought it up, Matthew exploded. He said, ‘I’ll always take care of our babies – and you!’"

Brazilian-born Camila, 26, has basically shelved her modeling career since moving in with the movie hunk in 2007. Their son Levi is 18 months old, and she gave birth to daughter Vida on Jan. 3.

And after Matthew shut her down, Cam went crying to her mother, said the source.

"Now Multo is pressuring Cam to get Matthew to commit to a legal agreement," the source revealed. "She said, ‘He wanted you to carry his babies – he ought to take real responsibility.’"

But the idea of signing a contract with Camila isn’t sitting well with Matthew, said the source, although the actor’s publicist denies the couple is having a disagreement.

The source revealed: "It’s caused a rift between them, and Matthew’s kind of scratching his head over it. He told me, ‘It seems kind of cold, doesn’t it?’

"But he’s got to realize that when couples love each other, they usually get married."