Disable portal use, contacts or accounts

Hi,

Is there anyway to disable or deactivate either portal use for a contact, the actual contact or an entire account?

We need to be able to disable system access for accounts for things like overdue support payments but don't want to delete the accounts / contacts as they will likely be brought back online in future and we still want to keep the tickets in the system for historical reporting.

Can you advise how I can achieve this?

Thanks,
Scott