Former Green Party leader Caroline Lucas called on Jeremy Hunt to resign as she marched with more than 1,000 striking doctors and their supporters through central London.
Ms Lucas joined the mass protest and it walked past the Houses of Parliament.
She said: “I have been expressing my support for the junior doctors right from the beginning.
“Jeremy Hunt has a huge amount to answer for.
“I also feel sorry for the patients as if you’re in pain it’s never nice to be in pain for a longer time.”
She added: “I think it’s awful that he [Hunt] refused to pilot the contracts.
“He must be wanting this strike in some way.
“I think he should resign now. I think he’s lost the trust and confidence of the doctors.”
She affirmed this statement in a speech outside the ministry of health, adding: “Jeremy Hunt must go!”