Nobel-winning economist Joseph Stiglitz has resigned from an advisory panel to Panama’s government set up after the Panama Papers scandal, citing lack of transparency within the committee.

The government set up the commission to investigate Panama’s financial practices after a massive leak of 11.5 million documents from law firm Mossack Fonseca in April revealed huge offshore tax evasion.

Stiglitz and Swiss anti-corruption expert Mark Pieth joined a seven-member commission, but both quit on Friday, saying that Panama refused to guarantee that the committee’s final report would be made public.

“I though the government was more committed, but obviously they’re not,” Stiglitz said. “It’s amazing how they tried to undermine us.”

In a statement, Panama’s government said it regretted the resignations of Stiglitz and Pieth, but claimed they were the result of unspecified “internal differences”.

“We thank them for recommendations they had already made and remain committed to transparency and international co-operation,” it said.

Panamanian president Juan Carlos Varela said in April that the commission would review the country’s notoriously opaque financial and legal practices.

In its first full meeting in New York on 4 and 5 June, the committee members agreed that the government of Panama needed to commit itself to making the final report public, whatever its findings, Stiglitz and Pieth said.

However, they said that they received a government letter last week that rescinded its earlier promise.

“We can only infer that the government is facing pressure from those who are making profits from the current non-transparent financial system in Panama,” Stiglitz said.

“I have had a close look at the so called Panama Papers and I must admit that, even as an expert on economic and organised crime, I was amazed to see so much of what we talk about in theory was confirmed in practice,” Pieth said.

He said he found evidence in the papers of crimes such as money laundering for child prostitution rings.

Stiglitz warned that the remaining five members of the committee may stop work on the investigation as well, and urged the international community to pressure Panama to improve transparency.

“We’re being asked to do this as a courtesy for them and we’re paraded in front of the world media first,” Pieth said. “Then we’re told to shut up when they don’t like it.”