Congress suffered a setback when three-time party MP and a staunch loyalist of the 'Nehru-Gandhi' family Rajkumari Ratna Singh joined the BJP on Tuesday.

Ratna Singh, who represented the Pratapgarh Lok Sabha seat in 1996, 1999 and 2009, was the daughter of former union minister Raja Dinesh Singh, the ex-ruler of the Kalakankar estate in Pratapgarh district in UP.

She hailed from the family of Raja Rampal Singh, who was one of the founding members of the Indian National Congress (INC). She had contested the 2014 and 2019 LS polls on Congress ticket but had lost.

Ratna Singh, who shared the stage with UP chief minister Yogi Adityanath at an election rally in Pratapgarh Sadar assembly constituency, where a by-poll was slated next week, said that thousands of her supporters had also joined the saffron party with her.

According to the sources Ratna Singh was ''upset'' over being ignored while reconstituting the state Congress committee by party general secretary Priyanka Gandhi Vadra recently.

''It appears that Ratna Singh was not happy at the humiliation of senior party leaders,'' said a senior UP Congress leader here while speaking to DH.

In the new PCC constituted by Priyanka, the senior leaders were made members of the 'advisory committee' and preference was given to the young and fresh faces.

It was not clear if she had been promised any ''political reward' in return but sources said that the saffron party might have assured nomination to her son in the next assembly polls in the state.

There were speculations that Congress MLA from Raebareli Aditi Singh, a one time loyalist of Rahul Gandhi, could also switch sides in the near future. Aditi had been served a show-cause notice after she attended the special UP assembly session in defiance of the party directive.

Ratna Singh's desertion comes barely a few months after senior Congress leader and the ruler of the erstwhile princely estate of Amethi Sanjay Singh, another Gandhi family loyalist, joined the BJP.