MOSCOW — Warning that the Soviet Union's deepening economic crisis is now threatening its political reforms, President Mikhail S. Gorbachev's chief economic adviser set out an urgent, step-by-step plan Monday for transforming the country's economy into one of "market socialism."

Deputy Prime Minister Leonid I. Abalkin, opening a national economic conference, said the country is rapidly running out of time if the whole reform effort is to succeed. He said that the economy must become the No. 1 political priority.

Popular discontent is rising over severe consumer shortages and higher prices, Abalkin acknowledged. Most people say that \o7 perestroika--\f7 restructuring--has done nothing to raise their living standards and perhaps made them worse, he said, adding that confidence in the Communist Party leadership is declining.

So severe is the crisis--the economy grew at an annual rate of only 1% in the third quarter, and winter is setting in without adequate stores of fuel and food--that there is again talk of sweeping, though unspecified, "emergency measures" to get the nation through the difficult period ahead.

"We are in risk of a creeping return, an unseen return," Abalkin said of pressures on the leadership to revert to the old political system in order to get quick results on the present economic problems. "You won't find anyone who advocates a return to the old system, but inch by inch, an 'instruction' here and an 'order' there, a real return develops."

Other economists, distinguished largely by their degrees of pessimism, agreed. "The situation is dangerous," said Stanislav S. Shatalin, another leading Soviet economist. "The threat is grave."

And Abel Aganbegyan, rector of the Academy of the National Economy, said the government had "underestimated the danger of the current situation on the consumer market."

"Urgent measures are those that are felt by the people," Aganbegyan said, calling for steps that would put consumer goods into the shops immediately. "Those measures with no effect, that exist only on paper, are not real measures. We need to act at long last to remove the imbalance caused by unsatisfied (consumer) demand."

Despite their agreement on the severity of the crisis, its political implications and even its causes, Soviet economists have differed sharply on how to get out of it. Achieving a consensus on long-term strategy and immediate tactics is a major aim of the three-day conference, in which Gorbachev and other members of the ruling Politburo are participating.