Europe’s hard-fought agreement to cap budget deficits, reached last week in an all-night emergency summit, got caught up in the French presidential campaign Monday, casting doubt on whether France will ever put it into practice.

President Nicolas Sarkozy’s main challenger in presidential elections next spring, Francois Hollande of the Socialist Party, declared that the accord is inadequate and that, if elected, he would renegotiate it “to put into it what is lacking today: efficiency with respect to the financial markets.”

“The treaty will not be ratified by France” if Hollande takes power in May, added Benoit Hamon, a key Hollande aide and the Socialist Party spokesman.

Moreover, Hamon said, France will not be the only country to withhold approval for the accord, reached early Friday morning after hours of talks but still being digested by financial markets in Europe and the United States.

The stand by Hollande marked an embarrassment for Sarkozy, who initiated the pact along with Chancellor Angela Merkel of Germany. After the summit in Brussels, 26 of the European Union’s 27 members adopted the deal, with Britain refusing to go along and several other governments cautioning that they had to consult their national parliaments before finalizing their adherence.

Sarkozy and Merkel called it the last chance to save Europe’s common currency, the euro, amid growing pressure on European Union governments with unmanageable debts. In an interview published Monday, Sarkozy again said there was no other choice and asserted that the bargain “creates the conditions for a rebound and a way out of the crisis.”

Hollande’s comments came the same day that former Prime Minister Dominique de Villepin announced that he plans to run for president as an independent, the Associated Press reported. Villepin has also criticized the European treaty, the AP said.

The agreement put forth by Sarkozy and Merkel calls on E.U. governments to reduce their budget deficits to a maximum of 3 percent of gross domestic product, with an eye to reducing their debts to 60 percent of GDP. Given the deficits and debts currently on the books in Europe, that would strain budgets to the limit and implies cutbacks so stiff that they might be politically impossible.

“I would like to say [the crisis] is completely put aside,” Sarkozy said in his lengthy interview with Le Monde newspaper. “But I will avoid doing so. We did everything it was possible to do. In a perfect world, theoretically, we should have done more, but the sign of a public servant, of a statesman, is to work with realities. That being so, this summit marks a decisive stage toward European integration.”

But Hollande, in a radio interview, said the accord dooms Europe to years of austerity budgets and reductions in social services. Instead of calling for low deficits, he said, it should have pushed the European Central Bank into becoming a bank of last resort for heavily indebted governments and made possible the issuance of European bonds to spread the debt around.

In addition, he said, steps should be taken to stimulate growth rather than cut budgets. Only with growth, he explained, can Europeans live better while their governments take in more tax revenue to whittle down debts while continuing to provide public services.

The European Central Bank, which under its statutes is independent from E.U. governments, has refused to buy up European debt, saying it is barred from doing so by the treaty that set it up. In addition, Merkel has refused to urge the bank to do so, saying that would infringe on its independence. Similarly, Merkel has balked at endorsing European bonds, pointing out that they would in effect force Germany’s robust economy to finance governments that have rolled up debts over the years to finance comfortable social protections without raising taxes.

Hollande, in his broadcast interview, did not say how he would overcome those obstacles, which Sarkozy also battled before giving in to Merkel.

Hollande’s pledge to renegotiate the treaty raised the danger that it would fall apart if he won the election. Opinion polls over the past several months have shown Hollande with a comfortable lead over Sarkozy in an election that ends with a second round in May.

Sarkozy’s backers in the Union for a Popular Movement (UMP) jumped on the statement, calling Hollande’s pledge “crazy” and “adventurous.”

“Francois Hollande’s proposal will be used against France and Europe by all those who do not want an agreement, such as the Britons,” Philippe Juvin, a UMP leader, said in a communique. “This declaration in reality is due to one thing. Francois Hollande does not know Europe.”