The Pakistan Cricket Board has made a formal complaint to Sky Sports after it broadcast an interview with Imran Khan’s sons, Kasim and Sulaiman, during its coverage of the first day’s play of the second Test at Lord’s.

During the interview Khan’s children raised concerns about the Pakistan government’s treatment of the country’s former prime minister, who has been held in solitary confinement for the past three years.

Kasim Khan said: “It is not very clear what they are doing, just blatantly trying to kill him in there. Keep him in as long as possible, and silence him.”

Khan’s lawyers have described his living conditions as slow-motion murder, while his sister has claimed he has been tortured while in prison. The 73-year-old was moved to a hospital last week for treatment after a supreme court ruling permitted his temporary release, but has since been returned to prison.

The precise nature of the PCB’s complaint is unknown other than the fact that Sky gave a platform to individuals critical of the government.

Sky has acknowledged the complaint, but declined to comment when contacted.

The England and Wales Cricket Board (ECB) has also been made aware of the PCB’s grievances, but declined to comment. Khan’s plight has also been highlighted by many of the world’s great former cricketers, who have written two joint letters “for humane treatment and proper medical care”.

After publishing their first letter in February the group, which includes six former England captains, the ex-India captain Kapil Dev and the former Australian batters Adam Gilchrist and Greg Chappell, issued another this week calling for “a full and independent assessment of his health”, particularly on his right eye.

Khan’s lawyers have said he has lost 85% of vision in his right eye as a result of his living conditions.

No Pakistani cricketers signed the letter.