Mr Ramesh said Ms Gandhi followed her 'mann ki baat' and implemented it seriously.
Speaking at the 'Times Literary Festival' in the capital city, on the topic of 'Indira Gandhi and Environment', he said the late prime minister was a very accessible leader.
"Gandhi also was a great believer in 'mann ki baat', but her 'mann ki baat' was a listening 'mann ki baat' not a speaking 'mann ki baat'. When she did 'mann ki baat', she listened, she didn't pontificate," said Mr Ramesh.
"She didn't tell the other person that she had all the answers to all the world's problem... entire environmental odyssey was a 'mann ki baat', but a listening 'mann ki baat'," he said, without mentioning PM Modi.
"She would take action on letters received from people, which shows that she was personally and instinctively committed to the cause of the environment," he said.
This was before the age of Twitter, Facebook, Instagram, and emails, Mr Ramesh said.
Talking about Ms Gandhi's inclination towards environment, Mr Ramesh said she was India's "first and last prime minister to have this great passion for nature conservation and environmental protection."