The 84-year-old Koirala was admitted to the intensive care unit with breathing troubles on Monday and still remains on oxygen.

The latest demand for an heir comes from Madhav Kumar Nepal, former deputy prime minister and chief of the Communist Party of Nepal-Unified Marxist Leninist, the second largest party.

At a public function in the capital on Saturday as well as at a separate meeting with leaders of Koirala's Nepali Congress party, Nepal said the prime minister's failing health has been holding up important state decisions and creating uncertainty and instability.

Accusing the new government, in which his party is a partner, of not being able to deliver, Nepal said: "The country can't be held prisoner to indecision because of the PM's illness...Responsibilities have to be transferred."

Last week, Koirala was to announce the government's plans and policies in parliament. But it had to be put off due to his illness. Since April, when he was made prime minister for the fifth time, the former chain smoker has been dogged by respiratory problems, requiring a trip to Thailand for medical treatment.

Before Nepal spoke out, the general public as well as the media have been asking Koirala's party to choose his successor.

"It's time to think of a future beyond Koirala," the Nepali Times weekly said in its editorial in its recent issue.

"The man is 84 and is on oxygen... His lung is malfunctioning and he has prostate problems. He was too ill to take oath of office in April, too ill to attend parliament's historic post-reinstatement session and now too ill to deliver the all important pre-budget speech in parliament...Whoever emerges as leader, the search must begin immediately."

However, it won't be an easy task.

Currently, there are two deputy prime ministers from two different parties and even choosing an acting prime minister could run into trouble. Last month, when Koirala was away in Bangkok for less than fortnight, the two deputies had a spat over who should head the government.

There would also be a strong tussle in Koirala's own party. Though going by protocol, either the vice president, Sushil Koirala, or general secretary Ram Chandra Poudel should head the Nepali Congress after Koirala, neither has his charisma and almost dictatorial ability to swing mass support.

Also, in the last few months, Koirala's nephew Shekhar Koirala has been rapidly advancing in the party hierarchy to the resentment of old timers. It remains to be seen if he would be a serious contender.

Finally, though Koirala continuously opposed King Gyanendra's power takeover since October 2002, when the king sacked the government, he is also the only one who has advocated retaining monarchy and has been the point of contact between the palace and the parties.

It remains to be seen if his heir would be able to maintain the same fine balance on the tightrope.