However Singh, an independent MP from Etah constituency, could not join the party himself due to the electoral clause under anti-defection law that requires him to first resign from the membership of the House.
The merger was announced by Kalyan's son Rajvir in a rally attended by BJP's top-brass leaders including national president Nitin Gadkari, Rajnath Singh, Mukhtar Abbas Naqvi, Uma Bharti, Kalraj Mishra and Vinay Katiyar.
Later talking to reporters, Kalyan said he is not joining the party right now as it will require him to resign from Parliament, thus necessitating a by-election which is unnecessary as the general elections are due in 2014.
Kalyan lashed out at Union Home Minister Sushilkumar Shinde for his remarks on BJP and RSS during the Congress conclave in Jaipur, and sought an apology from both Prime Minister Manmohan Singh and Congress President Sonia Gandhi over the issue.
"Prime Minister Manmohan Singh and Congress President Sonia Gandhi should apologise to the Hindu society for the minister's statement," he said.
Hitting out at parties "engaged in Muslim appeasement" for electoral benefits, Kalyan said BJP is not against the Muslim community and all it wants is a policy of justice to all.