Congress MP Rao Inderjeet Singh, who had demanded a probe into land deals of Sonia Gandhi's son-in-law Robert Vadra, Thursday formally joined the Bharatiya Janata Party (BJP).The MP from Gurgaon and rival of Haryana Chief Minister Bhupinder Singh Hooda, Rao Inderjeet joined the BJP with his followers at its office here.Addressing the gathering on the occasion, BJP president Rajnath Singh welcomed Rao and his supporters from Haryana into the party, and said it was a honour that Rao, who enjoys a clean image and hails from a martyr's family, is now part of his organisation.Rao Inderjeet's great-grandfather Rao Tula Ram was one of the noted freedom fighters during the 1857 revolt, while his father Rao Birender Singh was chief minister of Haryana.He said he will now be part of the BJP for rest of his life. He said it was not an easy decision to quit the Congress after serving the party for 36 years.Singh, who was elected to the Lok Sabha in 1998, 2004 and 2009, started his career in state politics by becoming a legislator for the first time in 1977.He also merged his newly formed political party "Haryana Insaf Congress" with the BJP.