Convicted former prime minister Thaksin Shinawatra is seriously ill and must remain in Police General Hospital as a return to jail could endanger his life, according to the Department of Corrections.

The department said on Thursday that it moved Thaksin to the hospital on Aug 23 because he needed continuous treatment and observation for many illnesses.

The Medical Correctional Hospital lacked equipment for his treatment, the department said.

The statement came a day before a planned visit to the hospital by a House committee seeking to verify Thaksin’s condition in response to growing public scepticism and official silence. It was not clear whether hospital authorities would let them go to the 14th floor where Thaksin is said to be staying.

The head of the Department of Corrections must approve any stay longer than 120 days by an inmate in a medical facility outside a prison hospital, and the minister of justice must acknowledge it. In Thaksin’s case, the 120-day deadline passed on Dec 21 without any news.

The statement said that officials at the Bangkok Remand Prison “recently” asked Police General Hospital about the condition of the 74-year-old inmate. The hospital replied that specialist doctors were treating him and he needed close care until his critical conditions could be resolved.

The director-general of the Department of Corrections on Monday extended Thaksin’s stay at the hospital. The statement did not say when the extension would end.

Opponents still plan to rally at Government House from Friday evening until Sunday to protest against Thaksin’s extended stay at the hospital.