He was the founder and chief of the Rashtriya Lok Dal, a political party recognised in the state of Uttar Pradesh.

He was made general secretary and a member of central parliamentary board of Lok Dal.

[8][9] Within months of joining politics, he removed Mulayam Singh Yadav from the position of Lok Dal legislature party leader in Uttar Pradesh Legislative Assembly.

[10] In 1989, he was General Secretary of Janata Dal after all the parties decided to merge under the leadership of VP Singh to take on the Indian National Congress.

[3] At several occasions, Ajit Singh was a significant political figure in government formations as well as in alliances.

[citation needed] He was elected to Lok Sabha (the lower house of Indian Parliament) from Baghpat in 1989.

[3] After his party joined the ruling United Progressive Alliance in 2011, he was Minister of Civil Aviation from December 2011 to May 2014.

[3] In 2019 Indian general election, He contested from Muzaffarnagar but lost to Sanjeev Balyan of BJP by a very small margin of 6526 votes.