The body of Dr David Kelly, the government chemical weapons expert who killed himself in 2003 after being outed as the source of a BBC story, has been exhumed, police have confirmed.

The scientist’s family reportedly had his remains cremated after asking for the grave to be dug up because they were upset it was being “desecrated” by conspiracy theorists who believe Kelly was murdered.

According to the Sunday Times, a source close to the scientist’s relatives claimed the Justice for Kelly campaign group placed placards and notes by the grave and held vigils there, upsetting Janice Kelly, his widow. “[She] hated it, she felt it was a desecration, and asked the police to get them to stop,” a family source told the newspaper.

The campaigners admitted to putting a placard calling for an inquest by the grave but insisted they had not desecrated it.

“We have been at this for four and a half years,” said Gerrard Jonas, of the campaign group. “We did put placards, one placard, asking for a coroner’s inquest. There has been no desecration. About three years ago Mrs Kelly sent the police round to me one Saturday night. They started questioning me.”

He told the Sunday Times: “Dr Kelly’s body was ... removed in the last week of July, headstone and all. They dug it up overnight. It was all done in haste. What looked like pieces of the coffin were left behind.”

Kelly’s body was found on 18 July 2003, a day after he had gone for a walk near his home. He had been exposed as the source of the report alleging that the government’s dossier on Iraq’s weapons of mass destruction, presented as central to the case for war, had been “sexed up”. The Hutton inquiry found he had killed himself, though there has been no inquest into his death.

A spokesman for Thames Valley police said: “The body of Dr David Kelly was exhumed a few months ago at the request of his family.”

The licence for the exhumation was granted by the chancellor of the diocese of Oxford. A spokesman said: “There is a presumption that Christian burial is permanent and that remains should not be portable. Therefore, a faculty for exhumation is only granted in exceptional circumstances. The body of Dr David Kelly was exhumed at the request of his family.”