He said that in his view former union minister Kamal Nath should be the party's choice for Leader of Opposition in the Lok Sabha if Rahul Gandhi does not accept the role.
Karan Singh said comparison between Narendra Modi, 63, and Rahul Gandhi, 43, was not fair. Also the Bharatiya Janata Party's campaign for the Lok Sabha election was "brilliantly and meticulously organised" and "clearly outdid" the Congress, Karan Singh, 83, told IANS in an interview.
Karan Singh, who is a Rajya Sabha MP and among the seniormost Congress leaders, said he had suggested to party president Sonia Gandhi that Rahul Gandhi, her son, should join the United Progressive Alliance government.
Asked if Rahul Gandhi should have accepted offers of former prime minister Manmohan Singh to join his government, Karan Singh said: "I think so. I had suggested to Sonia-ji that he should join the government."
He said Rahul Gandhi "was not willing" to join the UPA government.
Asked if it was a mistake, Karan Singh said: "Yes, in a way because he would have got some administrative experience of how to run a government. It was his choice. You can't force somebody to do something that they don't want to do."
Asked how Rahul Gandhi fared in comparison to Modi, who is now prime minister, in the Lok Sabha election, Karan Singh said it was not really a fair comparison. Modi was a very experienced politician who had been thrice elected as chief minister. "(He) is a very eloquent speaker, a very forceful personality."
"He (Rahul Gandhi) needs more administrative experience, political experience. He will learn. Five years in the opposition are the best classroom for any politician. When Rajiv Gandhi was in opposition, he was growing everyday. If he had not been assassinated, he would have come back and would have been a much better prime minister in his second term," Karan Singh told IANS.
"I am sure Rahul will learn a lot in the next five years sitting in the opposition. He will mature," Karan Singh added.
Karan Singh termed the Congress performance in the Lok Sabha election as "shocking" and said "we never expected that it will fall to such a low number".
Congress sunk to its worst Lok Sabha performance and could win only 44 seats in the 545-member lower house of parliament. The party failed to open its account in many states and did not touch double-digit in any state. Asked about the reasons for the party's debacle, Karan Singh said it was a combination of factors.
"There was a 10-year anti-incumbency. Then there were these huge scams or whatever you call them which gave the impression that everything was not being done in a transparent manner. Perhaps price rise also was another factor."
Karan Singh said there were some indiscreet remarks by certain party leaders.
"Mani Shankar Aiyar's statement about tea seller (jibe at Narendra Modi) was not necessary," he said.
Karan Singh, who first became union cabinet minister in 1967 under Indira Gandhi, also said that BJP's campaign was "brilliantly organised".
"They had everything tied up. They had media. Narendra Modi addressed 400-500 meetings. Everything was meticulously organised. Crowds were there, everything was on time. Sheer technology of running an election of this type, I think they clearly outdid us," he said.
A former 'Sadar-e-Riyasat' (head of state) of Jammu and Kashmir and a former ambassador to the US, Karan Singh is president of the Indian Council for Cultural Relations. He is also a reputed academic and a renowned orator. Karan singh was catapulted into political life at an early age of 18 when, on the intervention of then prime minister Jawaharlal Nehru, his father Maharaja Hari Singh appointed him regent.
Karan Singh, who has been in the Congress since 1967 and is widely respected as a senior leader, said the party "needs to do something to snap out of the negative syndrome" because its vote share was not as bad as its tally.
"We must see how do we hold on to the over 10 crore votes we have got and try to get in due course more support," he said.
Asked if Rahul Gandhi should be leader of opposition in the Lok Sabha, Karan Singh said he has a lot of organisational work in hand.
"Leader of Opposition is a full time job. You are pretty much stuck in parliament. So let's see. It is for him to decide. Sonia-ji to decide," he added.
"My personal view is that Kamal Nath should be (leader of opposition). He is into his ninth term in Lok Sabha, was parliamentary affairs minister and is bilingual."
Asked about demands that Priyanka Gandhi Vadra should take up a formal role in the party organisation, Karan Singh said it would help the party. "Certainly if she is interested, if she is willing it would help the party. She is young and intelligent and articulate," he said.