Proudly South African was established in 2001, born out of the 1998 Presidential Job Summit convened.
SABC news reported that Mantashe raised concerns about the "party political platform", which businesswoman Mamphele Ramphele launched on Monday.
"The worry that we are raising... is that when these initiatives were announced, the founder was in the United States and announced that she is raising funding," Mantashe said.
"Our biggest worry about that funding channel [structure]... is that half the time it is not channelled to strengthen government and in fact it is [used] to destabilise."
Ramphele has called her party political platform Agang SA, which means "build South Africa" in Setswana.
She said she intended using it to contest the 2014 national elections.