The incident occurred on a stretch on the Solapur-Barshi road when the minister was travelling in his car.
When contacted, Mr Shinde told PTI that he urinated in the open as he was feeling ill after spending nearly a month touring the state for the government's flagship Jalyukta Shivar scheme.
"I have been travelling continuously from the last one month taking review of the Jalyukta Shivar scheme. Continuous travelling in high temperatures and dust made me ill. I was suffering from fever today and when I couldn't find a toilet while travelling, I had to relieve myself in the open," Mr Shinde said.
"It is now proved that the government has been looting people in the name of Swacch Bharat cess on petrol and diesel," NCP spokesperson Nawab Malik said.
"How can the Prime Minister expect people to follow discipline when his own ministers are a bunch of undisciplined people? If the minister did not find a toilet on a highway, it means the government has all along been looting people in the name of Swacch Bharat cess on fuel. The minister has proved that the whole scheme is nothing but a big failure," Mr Malik said.