The announcement, which comes just ahead of the Lok Sabha polls, was made here by the party's zonal coordinator Vijay Pratap who claimed that the couple "failed to pay heed to repeated warnings about abiding by the party discipline".
However, the couple claimed that the action was taken "at the behest of Keshri Devi Patel", a former Zila Panchayat Chairperson who is the BSP's likely candidate from Allahabad Lok Sabha constituency.
"Patel has been systematically conspiring against all those whom she considered a threat to herself. She has been responsible for the sacking of many dedicated party workers. Now we are at the receiving end," the Guptas said adding that they "still have great respect for party supremo Mayawati who appears to have been misled by her colleagues".
Nandi, a businessman-turned-politician, had joined the BSP barely a few months ahead of the 2007 assembly polls in the state, wherein the predominantly Dalit-based party was seen building a broader social coalition which included upper castes, especially the Brahmins and the Vaishya community.
The party went on to win an absolute majority in the polls which also saw Nandi pulling off a sensational victory in Allahabad (South) against heavyweights like BJP's Keshri Nath Tripathi and Rita Bahuguna Joshi of the Congress.
He was rewarded with a cabinet berth by Chief Minister Mayawati, causing dissatisfaction among those who were ignored despite a long association with the party.
Nandi's political career, however, hit several roadblocks thereafter. A bomb attack outside his residence here in 2010 left him incapacitated for several months and the sympathy wave could not prove to be sufficient in the 2012 assembly elections in which he lost to his Samajwadi Party rival by a slender margin.
The local bodies polls held a few months later brought some good news as Abhilasha became the youngest Mayor of the city.
Meanwhile, sources close to the former BSP leader claimed that Nandi was planning to join BJP as the party was expected to regain lost ground in the state in the upcoming Lok Sabha elections.