Four opposition parties jointly submitted a bill Friday to the Lower House that would greatly reduce medical costs that hepatitis B and C patients need to shoulder for expensive interferon treatment and antiviral medication.

Last April, the government started subsidizing the interferon treatment for hepatitis B and C patients after admitting responsibility for approving tainted blood products that further spread the already rampant diseases in Japan.

But the opposition parties — the Democratic Party of Japan, the Social Democratic Party, Kokumin Shinto (People's New Party) and the Japanese Communist Party — argue that medical costs are still too high and many patients have given up applying for the subsidized treatments.