Singh's comments at the launch of Mukherjee's book--'The coalition years--in the presence of Congress president Sonia Gandhi and her deputy Rahul Gandhi left the audience in splits.
"In 2004 when Soniaji chose me to become the prime minister, Pranabji was one of the most distinguished colleagues that I had.
"He had every reason to feel a grievance that he was better qualified than I was to become the prime minister, but he also knew that I have no choice in the matter," the former prime minister said as the audience, including Sonia Gandhi and Rahul, burst into guffaw.
Mukherjee wrote in his book that after the 2004 election victory there was intense speculation in the party about who would be the prime minister, but the consensus within the Congress was that the incumbent should be a political leader with experience in party affairs and administration.
"The prevalent expectation was that I would be the next choice for prime minister after Sonia Gandhi declined. This expectation was possibly based on the fact that I had extensive experience in government," he wrote.
Mukherjee also said that when he declined to join the government headed by Manmohan Singh, Sonia insisted on his being a part of it as he would be "vital to its functioning and also be of support of Singh".
Mukherjee, in his speech at the book release function, decribed the Congress as a coalition in itself, as it brings all ideas on one platform.
"It was difficult to have one coalition within and another outside. But that was done," he said.
Mukherjee said in the book he has described the coalition years and tried not to bring in any personal matters. He said running the coalition government seemed difficult but everything worked out smoothly.
Mukherjee said in writing the book about the coalition years of 1996 to 2012, he did not claim the objectivity of a historian, which he is not, but put down things while viewing them as a political activist.
Singh said with their relation smoothened, they ran the government as a cohesive team. He said history would record Mukherjee's great contribution to the management of Indian polity.
The former prime minister described Mukherjee as the "most distinguished living parliamentarian and Congressman", whom everyone in the party looked up to for discussing and resolving ticklish and difficult issues.
"He is a politician by choice. He is the greatest politician living in the country. I became a politician by accident when P V Narasimha Rao asked me to become the finance minister," he said.
Singh described Mukherjee and NCP chief Sharad Pawar as respected senior members of his government both of whom were of great calibre. He said if the UPA government ran smoothly, a large measure of credit would go to Pranab Mukherjee.
While Sonia Gandhi and Rahul did not speak nor sit on the dais, a number of leaders including CPI-M general secretary Sitaram Yechury, CPI Secretary Sudhakar Reddy, SP leader Akhilesh Yadav and DMK leader Kanimozhi spoke.
Akhilesh Yadav, in his brief speech, said Mukherjee's book would come in handy for young politicians like him when elections are due just like good notes ahead of exams.
He also said people look forward to another coalition as elections draw closer. Akhilesh, who was recently reelected the SP president, said people earlier dealt with his father Mulayam Singh Yadav but would now deal with him.
Yechury said Pranab Mukherjee has an "elephant-like memory", remark that prompted Sonia Gandhi to quip he had the memory of "two elephants".