Manmohan was the chief guest at the launch of former President Pranab Mukherjee's new book 'The Coalition Years: 1996-2012'.
While addressing the crowd, Manmohan Singh said, "In 2004, Sonia ji chose me to be the Prime Minister. Pranab ji was the most distinguished colleague that I had. I became a politician by accident when PV Narasimha Rao invited me to become Finance Minister. Pranab Mukherjee is a politician by choice and he is one of the greatest politicians living in our country".
"Pranab Mukherjee had every reason to feel a grievance that he was better qualified than I was to be PM but he also knew I had no choice in matter. Therefore that smoothened our relationship. We ran the government as cohesive team of which Pranab Mukherjee was the most imp member," Manmohan added.
Pranab Mukherjee and Manmohan Singh had worked together in various capacities since 1970.
Pranab Mukherjee was widely expected to be the Congress choice for the Prime Minister's post, after Sonia Gandhi declined to lead the government in 2004.
This is the first time Manmohan Singh has expressed his views in public and acknowledged the disappointment that Pranab Mukherjee must have felt.