The Bharatiya Janata Party on Saturday asked the Congress-Left nominee in the presidential election, Pratibha Patil, to respond to charges that she had shielded her brother in a murder case.

BJP spokesman Ravi Shankar Prasad told reporters that his party believed that the Congress was not qualified to speak on behalf of Patil.

On Friday, his party leader Sushma Swaraj had said the National Democratic Alliance would not fight her on personal issues but on ideology.

"There has been a persistent attempt to prevent any fair investigation into such a high-profile murder. Therefore, it is important that Patil responds to these disturbing questions because these facts are related to her and the resultant questions are also related to her," he said.

Prasad cited charges of Rajani Patil, widow of a slain Jalgaon district Congress leader, that the former Rajasthan governor had been protecting her brother, who she said had a hand in the murder of her husband.

"The BJP does not have the slightest doubt that the Congress leadership knew about all these steps," he said, referring to the woman's earlier letter to UPA chairperson Sonia Gandhi in connection with the case.

He alleged that Patil was chosen as the presidential candidate because of her loyalty to the Gandhi family.

"The vulnerability of the candidate was known. She was chosen because she was vulnerable." he remarked.

Asked whether the opposition would approach the Election Commission over Patil's candidacy, he said "It is an issue to be considered."

The BJP leader, who gave a detailed account of the different stages of the murder case, also referred to allegations that there had been a default in payment of Rs 17.70 crore-loan by the Sant Mukta Bai sugar factory of which Pratibha Patil is said to be founder-chairperson.

"In view of this reported default, a serious moral question arises whether a person involved with an institution which has indulged in such irregularities is fit to become the President," Prasad said.

Asked why the opposition has overnight changed its stand on allegations against Patil, the BJP leader said they were too glaring to be ignored.