The centre has sought a report on the alleged ill treatment of jailed Rashtriya Janata Dal (RJD) MP Mohammad Shahabuddin by prison authorities.
Shahabuddin is lodged at the Siwan jail in his home district in Bihar.
Central home secretary VK Duggal has reportedly asked the Bihar government to provide a comprehensive report after Shahabuddin made the allegations in a letter to Lok Sabha Speaker Somnath Chatterjee, official sources said.
Bihar Chief Secretary GS Kang, however, denied receiving any letter from Duggal.
Shahabuddin had written to Chatterjee demanding a probe into the incident in which he claimed he was assaulted by the Siwan jailor and district superintendent of police in his prison cell a few days ago.
The RJD has alleged that the Nitish Kumar government has hatched a conspiracy to kill Shahabuddin by deliberately denying him proper medical treatment for spinal problems inside jail.
State RJD president Abdul Bari Siddiqui said Shahabuddin's health was deteriorating, he is not able to eat or go to the toilet properly due to acute spinal pain.
"Shahabuddin should be given treatment immediately because he is seriously ill," said Siddiqui, who led a team of RJD leaders to meet the jailed MP two days ago.
Earlier this month, RJD chief and Railway Minister Lalu Prasad visited him in jail and enquired about his health. Lalu Prasad had also demanded proper treatment for him.
Siddiqui said Shahabuddin had failed to appear in a special court set up inside the jail on Thursday due to ill health. "Shahabuddin is not in a condition to be brought before the court and needs to be excused," his lawyers told the court.
The court was set up in jail for speedy trial of his pending cases.
A Lok Sabha member from Siwan since 1996, he faces charges in over 40 criminal cases, including those relating to murder, abduction and possession of illegal arms and stolen vehicles. He also faces charges of sedition.
Last month, Shahabuddin was shifted to Siwan jail from the high security Bhagalpur prison in the wake of a Patna High Court directive to speed up the trial of cases against him.