Force India are angry with Formula 1's governing body in the wake of a dispute about race numbers.
Before Barcelona, teams were told to include bigger and more prominent numbers on their cars' bodywork, and Force India were penalised for falling afoul of the directive.
The small Silverstone-based team fixed their livery for Monaco, but a Force India source told Auto Motor und Sport that "the sponsors were not happy".
Technical boss Andy Green confirmed: "Our car was deemed legal at all times in Barcelona, but suddenly after the race it was said we didn't comply with the rules."
Sporting boss Otmar Szafnauer added: "This is a serious precedent.
"It means every other team can do the same thing also in the technical area. According to this, something that was legal on Thursday is no longer legal on Sunday."
The season continues on Sunday with the Canadian Grand Prix.
