LOS ANGELES - A US judge on Monday barred defense attorneys for Michael Jackson's doctor, who stands accused of involuntary manslaughter, from calling the singer's former physicians as witnesses.

The move will hurt the defense team for Conrad Murray, which had hoped the other doctors would help support their theory that the "King of Pop" - who died in June 2009 at age 50 - was addicted to drugs.

Los Angeles Superior Court judge Michael Pastor agreed to a motion by prosecutors to exclude six of Jackson's former doctors - including his long-time dermatologist, Arnold Klein - from the list of approved witnesses.

In court papers filed on Monday, defense attorneys Edward Chernoff and Nareg Gourjian alleged that Klein "administered frequent intramuscular injections of Demerol to Mr Jackson for no valid medical purpose," and that Jackson "became physiologically and psychologically dependent on Demerol".

"I do not think it is relevant," Pastor said. He told the defense they could not make any reference to the 2003 search of Jackson's ranch in Santa Barbara county, saying that it had no bearing on his death.

Chernoff argued that the testimony would show that Jackson was "addicted to and withdrawing from Demerol" - a factor he said was "important to our defense" - but to no avail.

Pastor said he would allow testimony from two other doctors, Allen Metzger and David Adams. Murray's defense team says Jackson asked Metzger in April 2009 to give him an intravenous sedative, a request the physician refused to grant.

Adams meanwhile gave Jackson the anesthetic propofol - an overdose of which later led to his death - on four occasions in 2008, after the singer had oral surgery. Jackson also used the drug as a sleep aid.

Pastor also approved testimony from a nurse who treated Jackson in 2009.

Murray, the last doctor to treat Jackson, is on trial for involuntary homicide in Jackson's death on June 25, 2009. He was in charge of administering propofol to the star.

Murray faces up to four years in prison if convicted.

His defense team is expected to argue that Jackson gave himself an excessive dose of the drug while the doctor was out of the room at the singer's mansion in the affluent Holmby Hills neighborhood west of Los Angeles.

Jury selection will begin on Sept 8, with opening statements scheduled for the end of next month.

Agence France-Presse