The son of a West German diplomat failed yesterday in a court bid to block his extradition from England, where he is imprisoned, to the United States, where he is wanted on a charge of murdering his girlfriend's parents in Bedford County, Va.

Two London High Court judges refused to issue a writ of habeas corpus to free Jens Soering, who was arrested in England on a bank fraud charge, and block his extradition. Soering's attorney indicated he might appeal to the House of Lords, Britain's highest court.

The court rejected a defense argument that the correct legal procedure had not been followed for seeking assurances from the U.S. government that Soering would not face the death penalty if convicted. Britain does not allow the death penalty.

Soering, 21, is alleged to have planned with Elizabeth Haysom, 23, the killing of her parents -- Derek Haysom, 72, and Nancy Haysom, 53. The wealthy steel magnate and his wife were hacked to death at their home in March 1985.

Chief Magistrate Sir David Hopkin ordered Soering's extradition on June 16, but gave his attorneys the right to appeal.

Haysom did not fight extradition and was returned to Virginia. She pleaded guilty to being an accessory to the murder of her parents.