Police were investigating claims last night that Michael Jackson received a painkilling injection minutes before his death amid intense pressure to prepare for a series of lucrative comeback concerts in London next month.

A cardiologist who was allegedly with Jackson when he collapsed on Thursday was at the centre of a police inquiry amid claims that Jackson had been receiving daily injections of Demerol, a synthetic painkiller similar to morphine. The coroner confirmed that the doctor, named by Jackson’s business manager as Conrad Robert Murray, had not signed a death certificate. Detectives seized a car linked to Dr Murray, saying that it might contain drugs or other evidence, and spoke to him immediately after Jackson’s death. Charlie Beck, of the Los Angeles Police Department, said that they needed to question him further.

An unidentified man said in a telephone call to the emergency services released yesterday: “The doctor has been the only one here.” Detectives were searching Jackson’s rented home in the upmarket Los Angeles neighbourhood of Holmby Hills.

Brian Oxman, the Jackson family’s former lawyer, criticised “enablers” in his entourage for allowing him to abuse prescription drugs. “This was something which I feared and which I warned about,” said Mr Oxman, who was with Jackson’s sister La Toya and brothers Jermaine and Randy at the hospital. “This is a case of abuse of medication, unless there is another cause I did not know about.”

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The night before his death Jackson was rehearsing for 50 concerts due to start at the O2 arena in London on July 13. Uri Geller, the self-styled psychic and friend of Jackson, told Sky News: “Stress is a killer, any doctor will tell you that. I think the anticipation of this mammoth challenge that was coming upon him, doing these 50 concerts, wanting to be close to perfection when he was going to be on stage, put him under huge, huge pressure.”

Results of a post-mortem examination will be delayed while tests, expected to take up to six weeks, are undertaken, the coroner’s office said. A spokesman said that there was no evidence of foul play and that the singer had been taking prescription drugs.

Tohme Tohme, Jackson’s business manager, insisted that the singer was fit, despite having cancelled the first of a series of concerts at the O2.

Randy Phillips, chief executive of AEG, which owns the O2, said that Jackson had shown “pride and confidence” during rehearsals this on Wednesday night.

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