Samajwadi Party chief Mulayam Singh Yadav on Friday admitted that joining hands with former Uttar Pradesh Chief Minister and BJP leader Kalyan Singh was a "terrible mistake".Addressing supporters and party workers on the birthday of senior party colleague Bhagwati Singh, Yadav said he can now admit that joining forces with Kalyan Singh was a mistake and had cost the party dearly."It was because of the damage to the party that I withdrew (my support) later," he said, explaining why the Samajwadi Party severed ties with Kalyan Singh, now the Governor of Rajasthan.Yadav, however, clarified that he still had cordial relation with Kalyan Singh but the coming together of the two had created a rift within his own party. Yadav had allied with the former Bharatiya Janata Party leader ahead of the 2009 Lok Sabha election but the partnership fell apart after his party's poor performance.He later blamed his colleague and party general secretary Amar Singh for the alliance. However, Kalyan Singh clarified it was Yadav who sought his help.Kalyan Singh was the Chief Minister of Uttar Pradesh when a mob razed the Babri Masjid at Ayodhya in December 1992.