Taking a dig at Rahul Gandhi, S.M. Krishna, who has joined the BJP, said the politics is a serious business and not a "hit-and-run job".
The 84-year-old former external affairs minister said there is a disconnect between the Congress leadership and the rank and file of the party.
The comments by Krishna came a day after he joined the BJP.
He also praised Prime Minister Narendra Modi's zero tolerance approach towards corruption.
Amidst questions being raised over the leadership ability of the Congress vice president following the UP debacle, Krishna was asked about his views on Gandhi's working style.
"Politics was not a hit-and-run job nor is it a part-time job," he told PTI.
He also said that the Congress needed to be rebuilt but saw "no seriousness" on the part of its leadership.
"There is no connect between the Congress leadership and the rank and file of the party," he said.
After having spent nearly 50 years in the Congress, Krishna quit the party in January after expressing his unhappiness over being sidelined.
"I never demanded any post, just wanted to be respected for my seniority," he said.
His joining the BJP is also being seen as a major boost to the party, which is now looking to spread its footprint in southern India ahead of the Assembly elections in Karnataka next year.
Krishna, who belongs to the Vokkaliga community that accounts for 15 per cent of Karnataka's nearly 5 crore population, is considered an influential leader. The community dominates nearly 40 per cent of the seats in 224-member Karnataka Assembly.
