The question was asked to him by the moderator at the Eastern Economic Forum (EEF) and he replied that his saying 'yes' or 'no' would not matter since the poser has not come from the G-7.
"If such a question had come from the G-7, it would have been appropriate.. My saying 'yes' or 'no' to a question coming from you has no value," Modi told the questioner, a journalist.
At the same time, he said India, in principle, is in favour of a multi-polar world with equal powers and responsibilities.
The moderator was wondering whether G-7 should be expanded to G-10 by including Russia, India and China.
Answering this, Russian President Vladimir Putin said: "We can't imagine any influential international organization without India and China."
The G-7 comprises the US, the UK, Canada, France, Germany, Italy and Japan.
For a certain period, Russia was its member, making it G-8 but it ended in 2014.
Interestingly, Japanese Prime Minister Shinzo Abe was present when the question was asked at the Plenary session of the EEF.
Modi was the Chief Guest at the event, where he spoke about his vision of making a 'New India' with a target of making the country a $5 trillion economy by 2025.
He was on a two-day visit here since Wednesday.
( With inputs from IANS )