Nawaz Sharif's platelet count has increased to 20,000 from 2,000," PML-N leader Attaullah Tarar said.

Pakistan's former prime minister Nawaz Sharif's condition deteriorated because he might have been given ''poison'' in the custody of the anti-graft body, his son Hussain Nawaz alleged on Tuesday.

The three-time former prime minister and supreme leader of the PML-N was shifted to the Services Hospital Lahore late on Monday night after his condition deteriorated.

Nawaz Sharif, 69, is serving a 7-year prison term since December 24, 2018, when the accountability court convicted him in the Al-Azizia Steel Mills case - one of the three corruption cases filed in following the Supreme Court's 2017 order in the Panama Papers scandal.

"My father might have been given poison as his platelets were critically low when he was shifted to hospital," Hussain Nawaz tweeted from London.

He said the Imran Khan government will have to give an answer for not shifting Nawaz Sharif to the hospital on time despite his critically low platelets count - 16,000, as per his fresh medical reports.

"While a substantially reduced platelet count is in itself very serious and potentially life-threatening why his father was not shifted to hospital. Will the government explain this?" he asked.

A medical board headed by Dr Ayaz Mahmood on Tuesday examined Sharif at the hospital and transfused platelets to him.

"Nawaz Sharif's platelet count has increased to 20,000 from 2,000," PML-N leader Attaullah Tarar told PTI. He said doctors said that the condition of Nawaz Sharif is still "serious" and he will remain in hospital till it improves.

According to doctors, normal platelets count ranges between 150,000 and 400,000.

The National Accountability Bureau (NAB) under whose custody Nawaz Sharif is, said: "Nawaz Sharif's condition is stable now. He is getting treatment in the hospital and his condition is improving."