Quite often when there is communal parking, especially in new build properties there is a restriction (covenant or regulation) in the lease stating that only one vehicle can be parked and no commercial vehicles, caravans, camper vans etc... can be parked there.
Do you buy or rent? If you own it then check the lease you shold have been given a copy of when you bought.
If you rent then you could approach your landlord or letting agents to see if they can find out.
Is there a landlord or managing agents or a management company you can approach about it as they should be aware of what is contained in the lease and may be able to help with enforcement.
It may, however, be difficult for them to police (and they may not know unless anyone makes them aware) if it is a general parking area with no specific space allocated to each flat.
Maybe they could introduce something to stop abuse such as parking permits, one per flat, so it is obvious if someone is parking there who shouldn't be or more than one vehicle.