WARSAW, JULY 28 -- Many of Solidarity's best-known leaders today launched a political party that directly challenges Lech Walesa's drive to become president of Poland.

The creation of the party, called the Citizens' Movement for Democratic Action, formally splits the Solidarity movement into two competing political parties.

The 1,000 or so delegates to today's Citizens' Movement congress endorsed a constitutional amendment mandating a popularly elected president, and leaders of the group made it clear that they will run someone against Walesa.

Walesa, who heads a party called Center Alliance, wants immediate presidential elections. But he wants the choice to be made by the current parliament, rather than in a nationwide vote.

The split in Solidarity has been building for months as economic austerity and the defeat of a common Communist enemy have wedged apart the movement's decade-old alliance of professional and working classes.

Walesa, the charismatic anti-Communist crusader who led a united Solidarity in the 1980s, has transformed himself in recent months into a populist defender of Polish patriotism and the working man. His Center Alliance party has been critical of the Solidarity-led government of Prime Minister Tadeusz Mazowiecki, once a close friend of Walesa.

Walesa, who helped put together the present government last year, has accused it this year of reforming the economy on the backs of workers and of being too slow to flush former Communists out of the bureaucracy.

The Citizens' party that was announced today is being led by such prominent Solidarity members as newspaper editor Adam Michnik, filmmaker Andrzej Wajda and Minister of Labor Jacek Kuron. The party is the response of professionals, intellectuals and technocrats to what they describe as Walesa's "demagoguery."

The new party defends the government's "shock therapy" economic program. Such a program aims at stabilizing a market economy through reforms that create short-term but often widespread unemployment, shortages of consumer goods and a reduced standard of living.

"We know that this {the working} class is most severely touched by the austerity measures. But because of this, people of this class -- workers -- have to change their way of thinking," said Zbigniew Bujak, a key leader of the new party and a Solidarity activist who came to national prominence while working in a tractor factory near Warsaw.

"No longer will our society need a strong industrial working class. . . . These people have to think how to change the environment around themselves, how to build new working places in small workshops and small companies, how to show initiative," said Bujak.

As reforms have begun to bite this year, more than 600,000 people have become unemployed, and real incomes have fallen by more than one-third. But inflation is under control, and an extraordinary variety of consumer goods have begun appearing on traditionally bare Polish shelves. Western donors have given the government rave reviews, along with aid and a generous rescheduling of a $40 billion debt.

The Citizens' Movement says its presidential candidate of choice is Mazowiecki, the prime minister whose popularity in public opinion polls is nearly double Walesa's. But it is unclear if Mazowiecki wants to give up leadership of the government to take a position that, under current law, is largely ceremonial.

Supporters of Walesa's party increased the pressure for quick elections today by demanding the resignation of the current president, Wojciech Jaruzelski. Jaruzelski is the general who imposed martial law here in the early 1980s and is serving a six-year term as president.