Dr Ghazi Algosaibi condemned stories in British newspapers, saying: "This trial by press is not helping anyone, least of all the two nurses and their families."
He was speaking as it emerged that the brother of victim Yvonne Gilford said he was considering a plea for clemency, if the nurses were condemned by a court.
Frank Gilford said: "If they don't want to behead them and want to put them in prison, that would be all right with me. If they were locked away in a Saudi jail for the rest of their lives, I think it could be worse than actually being beheaded."
Dr Algosaibi defended the Saudi justice system, saying the case would be examined "thoroughly and fairly", adding: "No confession is valid unless given freely in front of the court.
"Even if they are found guilty, the death sentence is not automatic. The court will determine the appropriate punishment having taken all the circumstances into account." He said the nurses would have ample opportunity to defend themselves.
The ambassador added: "There will be no special arrangements for this case or any other. Until the court renders its judgment, all the reports must be dismissed as pure speculation.
"These nurses were charged, but must be considered innocent until the court finds them guilty."
British diplomats were last night holding discussions with Saudi officials over gaining access to the nurses, Lucy McLauchlan, 31, and Deborah Parry, 41, who are being held in Dhahran. It is thought that a consular official will not be able to meet them until tomorrow. The Foreign Office said it wanted a visit "as soon as possible" to arrange legal representation. It has asked the nurses to choose from a list of English- speaking lawyers.
A spokesman said: "We are still keen to see them. We will continue to press the Saudis. People in this sort of situation depend on consuls."
The pair were arrested a week ago after the death of Miss Gilford, 55, an Australian nurse at the King Fahd Military Medical complex, where all three worked. Her body was found in her room on 11 December. She was said to have been beaten and stabbed.Reuse content