European Commission President Jean-Claude Juncker has called his handling of the 2014 Lux Leaks one of the two biggest mistakes of his five-year term.

Speaking before a meeting of European leaders in Romania, Juncker, who previously served as prime minister of low-tax microstate Luxembourg for almost twenty years, said he was wrong not to have acted sooner.

“I should have responded immediately,” Juncker said, qualifying his reaction to the Lux Leaks scandal as a “personal” error. “That was a major mistake that I took too much time to respond to that.”

The second error was staying silent during the 2016 Brexit referendum, Juncker said.

Juncker’s mea culpa comes months before the end of his presidency. The 64-year old recently announced that he would not seek a second term beyond October.

The Lux Leaks investigation, a collaboration of more than 80 reporters in 26 countries, was published in November 2014, days after Juncker become European Commission president.

The exposé by the International Consortium of Investigative Journalists revealed how some of the world’s largest corporations piped billions of dollars through Luxembourg to avoid paying taxes.

Leaked documents brokered by accounting firms PricewaterhouseCoopers, Deloitte, KPMG and Ernst & Young showed that Luxembourg signed more than 300 secret tax deals with household-name companies, including Ikea, Skype, Pepsi and Disney.

In several cases, the deals — known as “tax rulings” — allowed companies to pay less than 1 percent tax in Luxembourg.

Weeks after the revelations, more than 100 largely far-right members of the European parliament voted to censure Juncker.

Margaret Hodge, member of parliament and chair of the United Kingdom’s public accounts committee said at the time of Juncker’s election: “He has just taken over the European commission, [yet] he’s presided over the biggest exploitation of European nations in his own little country for decades.”

Despite promises by members of Juncker’s Commission to examine the Lux Leaks revelations, ICIJ reported in February that, more than four years later, it had still failed to investigate a single Lux Leaks tax ruling.

The following month, the Commission responded by opening an investigation into the tax affairs of Huhtamäki, a Finnish packaging group that had featured in the Lux Leaks files.