A senior Conservative MP has written to the home secretary expressing his concern over the sudden death of a Sikh activist in Birmingham last year. Neil O’Brien, the MP for Harborough and a former minister, has written to James Cleverly questioning the death of Avtar Singh Khanda in June, which coincided with alleged Indian plots to kill Sikh activists in North America. His letter comes after the Guardian revealed that West Midlands police did not undertake a full investigation into Khanda’s death despite previously having said they had. O’Brien’s letter, which has been seen by the Guardian, says: “I have been extremely concerned by ongoing reports in the press about the death of Avtar Singh Khanda. West Midlands police seem to have originally said that his death at age 35 was investigated. “However, I understand his family are concerned that police did not take statements from friends or family; did not speak to his employers or work colleagues; did not retrace his steps on the days before his sudden illness; did not visit his residence; did not study threats made against him; did not issue a case number, which would indicate the matter had been investigated.” He added: “If this is correct, is it possible to find out from West Midlands police what their investigation consisted of, if not the actions above?” The Home Office did not respond to a request to comment. Khanda was a high-profile campaigner for a separate Sikh state known as Khalistan – a movement which India views as an increasingly serious threat to its own territorial integrity. In the last few months both the Americans and Canadians have accused Indian agents of trying to assassinate Khalistani activists last summer, around the time of Khanda’s death. Khanda was admitted to Birmingham’s Sandwell hospital in June, unwell and in pain. While there he was diagnosed with an aggressive form of blood cancer known as acute myeloid leukaemia and died two days later. His death was recorded as being natural, but Khanda’s friends and family have long viewed it as suspicious and have called for a formal inquest to be undertaken. For months the West Midlands police insisted it had carried out a thorough review of his death and found nothing suspicious. Cabinet ministers also referred to the police review when asked about the case by constituents. However, the Guardian revealed last year that the police did not take any of the actions normally associated with an investigation, including interviewing Khanda’s family or assigning it a case number. Instead, the force said it had referred the matter to the coroner and been “satisfied that there were no suspicious circumstances”. O’Brien’s letter is the first major intervention in the case by a senior British politician and will increase the pressure on ministers to investigate Khanda’s death more carefully. As MP for Harborough, O’Brien has one of the highest proportions of Sikh constituents in the country. In the letter O’Brien said: “While I obviously am in no position to judge the facts of this case, it is concerning that the bereaved family of this young man have been left feeling that his death has not been properly investigated, which much make it difficult for them to find peace.”