Prescription Plan Preservation Act of 2004 - Amends part D (Voluntary Prescription Drug Benefit Program) of title XVIII (Medicare) of the Social Security Act to condition the payment of Medicare employer prescription drug subsidies on the maintence of current prescription drug benefits.
Requires the actuarial value of prescription drug coverage to be at least equal to the greater of actuarial value of: (1) standard prescription drug coverage (as under current law); or (2) the employment-based retiree health coverage in effect as of December 8, 2003.