 Subsequently, other insurance companies have entered the top-up market and criticism has been levelled at the products from the union Unison which stated that the products would undermine the values of the NHS and risk creating a two-tier system in health care.WPA Protocol administers corporate healthcare trusts.This is an alternative arrangement to private medical insurance whereby larger companies, defined by Protocol as usually those with 400 or more members, can use WPA's infrastructure to administer their own healthcare provision.