The search warrant quoted Murray as saying that he had treated Jackson for insomnia for six months using propofol, regularly giving him 50 milligrams of the drug via an intravenous feed. Murray claimed that he had been trying to wean the pop star off the powerful drug, and on the day he died Jackson only received a 25-milligram dose.

The warrant exposed a potent drug cocktail that Murray had administered to Jackson in the hours before his death, including valium and other sedatives including lorazepam and midazolam and ofmidazolan. When none of these helped Jackson sleep, the doctor gave him the propofol diluted with painkiller lidocaine.

Murray told investigators he left the room for 10 minutes to use the bathroom, and when he returned Jackson was not breathing, the warrant said.

Chernoff denied the assertion: 'Murray simply never told investigators that he found Michael Jackson at 11.00 a.m. not breathing.'

'He also never said that he waited a mere 10 minutes before leaving to make several phone calls. In fact, Murray never said that he left Michael Jackson's room to make phone calls at all.'

Propofol is usually used only as a hospital anaesthetic, and the discovery of lethal levels in Jackson's system is likely to increase speculation that Murray will face manslaughter charges over the pop star's death.

Murray's records did not reveal any prescription for propofol, and it is unclear where Jackson obtained the drug, the affidavit said. Murray was quoted as telling investigators that Jackson had been treated with propofol by two doctors in Germany.