Lucknow, May 4: Sara Singh's mother and Madhumita Shukla's sister today threatened a hunger strike in front of the BJP headquarters in Delhi if the party inducted Independent MLA Amanmani Tripathi into its fold.

Amanmani, MLA from Nautanwa in Maharajganj, is accused of strangling his wife Sara to death in July 2015 and fabricating a car crash scene to pass her death off as an accident. He is out on bail.

His father Amarmani Tripathi, a former Uttar Pradesh minister, and mother Madhumani have been serving life sentences since October 2007 for the murder of Madhumita, a Lucknow poet, in 2003. Madhumita, 24, had been in a relationship with Amarmani and had refused to undergo an abortion.

Chief minister Yogi Adityanath had shared a stage with Amanmani at an event at Gorakhpur University last Saturday, where he publicly blessed the MLA.

Amanmani again met Adityanath on Sunday and later told reporters he was "prepared to join the BJP with the blessings of the chief minister".

Sara's mother Seema Singh, 60, today told reporters that the CBI, which is investigating Sara's murder, was under pressure to give a clean chit to Amanmani.

"The CBI is not probing the case properly because there is a BJP government at the Centre as well as in Uttar Pradesh," Seema said at a joint news conference with Nidhi Shukla, younger sister of Madhumita.

"This is the reason he is out on bail. It is frustrating to see my daughter's murderer with the chief minister. Nidhi and I shall sit on a hunger strike at the gate of the BJP office in Delhi if Amanmani joins the party."

Nidhi, who is in her mid-30s, said: "BJP leaders must come forward and react against Amanmani's statement that he will soon join the BJP. Otherwise we shall take it that they have no reservations against a killer joining the party."

Father Amarmani, a party hopper known for his strong-arm tactics and ability to engineer large-scale defections, had several criminal cases against him, including kidnapping charges. He had been part of the BJP, Congress, Bahujan Samaj Party and the Samajwadi Party.

The Samajwadi Party had fielded Amanmani in the 2012 Assembly elections but he had lost. When Akhilesh Yadav, battered by accusations of fielding too many alleged criminals, denied him a ticket at the last-minute before the February-March elections this year, he contested as an Independent.

Sara, 27, was found dead in a Swift Dzire near Firozabad, 286km from Lucknow, on July 9, 2015. Amanmani had purportedly been at the wheel but escaped without a scratch despite the car apparently rolling over a few times and falling into a ditch beside the highway. The case was handed over to the CBI after the autopsy suggested Sara died of strangulation.

Madhumita was shot dead at her home in Lucknow on May 9, 2003. The CBI proved in court that Amarmani and his wife had hired the two killers.