Addressing a press conference here, Gadkari, who is on a day's visit to the city, alleged the Congress had purchased 19 MPs to save UPA-1 during the trust vote in July 2008.
Gadkari said though Singh enjoyed the image of being a clean person, it was impossible that people could be sent to prison without his knowledge or consent.
The BJP president said he had known Sudheendra Kulkarni, former aide of LK Advani, for the last 30 years and it was improbable that a man like him could be involved in any wrong doing.
Pointing out that the Delhi High Court had made several comments on the manner in which people had been implicated in the cash-for-vote scam, he said BJP will raise the issue across the country.
On July 22, 2008, some BJP MPs had waved wads of currency notes on the floor of Lok Sabha during the trust vote faced by the UPA-I government, alleging they were given the money to vote in favour of the government.
Asked if Gujarat Chief Minister Narendra Modi would campaign for BJP in Uttar Pradesh Assembly elections, he said plans would be made for polls only after they were announced.
He said Chief Minister Mayawati's announcement to divide Uttar Pradesh into four states, was only a "gimmick" as she was aware that she would lose the upcoming elections.
"In any case new states are not formed through announcements by Chief Ministers but only by referring the matter to the State Re-organisation Commission," he said.
To a query, Gadkari said he had no ambitions of becoming Prime Minister and was content being an ordinary worker of the BJP.