MADRID - Spain's Prime Minister Mariano Rajoy has survived resignation calls over a party slush fund scandal but he is now vulnerable to an affair that refuses to go away, analysts and papers said Friday.

The financial scandal in the ruling, right-leaning Popular Party has outraged Spaniards suffering high unemployment, austerity measures and a recession.

But in a parliamentary grilling Thursday, Rajoy scorned opposition calls for him to step down. Political analysts and the press said the 58-year-old PM, who led his party to a landslide election win in Nov 2011, delivered a hard-hitting parliamentary performance. For the first time, Rajoy admitted making a mistake in trusting the Popular Party's disgraced former treasurer, Luis Barcenas. But he denied allegations that he received illegal payments himself and declared: "I am not going to declare myself guilty because I am not."

Many people would welcome the fact that Rajoy agreed to debate the scandal in parliament after months of damaging leaks in the press, said Cristobal Herrera, consultant at political communication advisors Llorente & Cuenca.

"A resignation is unlikely in the near future," Herrera said.

"Political stability is guaranteed because the government has an absolute majority in parliament and the Senate," he added.

It was impossible to say, however, whether new documents would emerge in judicial investigations into the affair that could force the prime minister's hand, he added.

Fernando Vallespin, political science lecturer at the Universidad Autonoma de Madrid, said Rajoy had no choice but to admit an error in his relationship with Barcenas after the publication of friendly mobile phone text messages he had sent to the former party treasurer.

"He can survive this legislature but his political career is already probably tainted," Vallespin said.

New leaks could yet emerge in the scandal, he said, "if not tomorrow then in the weeks ahead".

The corruption affair originated in 2009 as a judicial investigation into alleged kickbacks involving members of the Popular Party and construction companies.

It exploded in January when leading daily El Pais published copies of account ledgers purportedly written by Barcenas and showing irregular payments to top party members including Rajoy, its leader since 2004.

The noose appeared to tighten further around the premier's neck when Barcenas testified in court on July 15 that he handed cash to Rajoy.

Conservative newspaper El Mundo calculated that Barcenas paid a total of 343,700 euros (around $456,000) to Rajoy over two decades.

In an editorial Friday, El Mundo said Rajoy's strong parliamentary performance nevertheless failed to convince people that his party's finances were clean. "He did not provide any credible explanation for the Barcenas accounts," the paper said.

El Pais was equally unconvinced. "Without explaining in detail the evidence unveiled since the publication of the Barcenas papers, without promising an independent investigation, without accepting that his party may have benefited from irregular financing for 20 years and without promising that it won't all happen again, Rajoy dodged the worst moment of his prime ministership thanks to his great skill as a parliamentarian," El Pais said. "But the political crisis remains open," the paper added.

Barcenas was jailed in June pending an investigation into a separate corruption case, in which he is alleged to have held 47 million euros in secret Swiss bank accounts.