Zulfikar Ali Bhutto, the former premier of Pakistan who has been sentenced to death by the military regime, has gone on a hunger strike to protest his treatment in prison.

His lawyer also announced yesterday that Bhutto has one "last wish" - to read Richard Nixon's recently published memoirs.

The lawyer said that Bhutto has not eaten solid food for the past four days and that he has said he will not eat again unless or until his "humiliating and degrading" treatment is improved.

Bhutto, whose appeal against his death sentence opened in Pakistan's supreme court yesterday, is specifically demanding that he be allowed to exercise in the fresh air, that he be given some privacy while performing toilet functions, and that he be permitted to switch off and on his light and cooling fan.

Bhutto's attorney said that the former premier is currently permitted to exercise one hour a day but only in a prison corridor and that five guards are watching him all the time, even at the toilet. A report issued by Amnesty International last week questioned the conditions under which Bhutto is held.

"He is looking terribly thin," the lawyer said. "He is ill, and he is upset at the way they treat him. They seem determined to be a unpleasant as possible, on orders from the military above, of course."

The appeal, which began before the full nine-man supreme court, is expected to last for up to three months. Despite the presence of many foreign journalists and observers from international legal organizations, Bhutto was not permitted to attend.

The country's chief justice, Anwar Ul Haq, who presided over the case in spite of strenuous objections from Bhutto that he was biased, said that no useful purpose would be served by Bhutto's presence at this stage. He did, however, leave open the possibility that the former premier will be allowed to appear - "to help his lawyers" - in a later stage of the proceedings.

Bhutto and four others were sentenced to death last March by a court in Lahore, the capital of the Punjab, after being found guilty of conspiracy in the 1974 murder of the father of one of Bhutto's political enemies.

If the supreme court upholds the verdict and sentence, then it will be up to the governor of the Punjab, and finally the president of Pakistan (with, presumably, advice from Gen. Zia Ul Haq's military government) to decide whether the popular Bhutto should be executed.

The strategy to be pursued by his legal team, which is led by a former Pakistani attorney general, Yahya Bakhtiar, is to accuse the military government of falsifying records and to demolish the prosecution case for its "lack of real evidence."