"We congratulate him with great honour on receiving the Bharat Ratna," Singh told reporters in the state assembly.
Singh said though Vajpayee was not from Congress, but former prime ministers such as Jawaharlal Nehru and Indira Gandhi had great regards for him.
The senior Congress leader recalled how Vajpayee praised him thrice during the Chief Minister's conference.
Singh had arrived here to offer fruit juice to Congress MLAs who gave up their indefinite hunger strike on the issue of providing relief to farmers hit by rain and hailstorms.