Michael Jackson's doctor has been charged with involuntary manslaughter over the pop singer's death.

Prosecutors announced the charge against Dr Conrad Murray, a Houston cardiologist who was with Jackson when he died on June 25. He faces up to four years in prison if convicted.

Murray will plead not guilty, said his lawyer Ed Chernoff.

Jackson hired Murray to be his personal physician as he prepared for a strenuous series of comeback performances in London. Officials said the singer died in Los Angeles after Murray administered the powerful general anaesthetic propofol and two other sedatives to get the chronic insomniac to sleep.

Murray is accused of acting "unlawfully and without malice" in bringing about Jackson's death, according to a complaint filed by prosecutors.

The complaint said Murray acted "without the caution and circumspection required" when he administered a powerful sedative to Jackson in an effort to help the 50-year-old to sleep.

"We'll make bail, we'll plead not guilty and we'll fight like hell," Mr Chernoff said before the charge was filed.

Los Angeles investigators were methodical in building a case against Murray, wary of repeating mistakes which have plagued some other high-profile celebrity cases, most notably OJ Simpson and actor Robert Blake, both of whom were acquitted of murder.

After reviewing toxicology findings, the coroner ruled Jackson's death was a homicide caused by acute intoxication of the powerful anaesthetic propofol, with other sedatives a contributing factor. Propofol is only supposed to be administered by an anaesthesia professional in a medical setting, because it depresses breathing and heart rate while lowering blood pressure.

Murray appears to have obtained the drug legally and its use is not in itself a crime. To show the doctor was negligent in his care, detectives spoke to more than 10 medical experts to see if his behaviour fell outside the bounds of reasonable medical practice.