The consortium planned to release its report on the eve of a Thursday meeting of finance ministers from eurozone countries in Brussels, where the issue of Luxembourg’s preferential arrangements might be discussed.

Many multinationals have operations in Luxembourg despite its small size and a population of only about 525,000. But the country’s business model has prompted concerns among the European Union authorities that its policies create unfair advantages over other countries in the bloc.

On Friday, the eurozone ministers will be joined by their colleagues from all 28 European Union countries to discuss tax policies.

One country having lower tax rates than its neighbors is not against European Union rules. But it could be a violation if a country granted special deals to certain companies that were not available to others.

A spokesman for the Ministry of Finance in Luxembourg declined to comment Wednesday evening. But he said the country’s finance minister, Pierre Gramegna, planned to hold a news conference in Brussels on Thursday to address the issues raised by the consortium.

Last month, in response to the start of the investigation concerning Amazon, the Luxembourg finance ministry said that reports of so-called state aid were unfounded and that “the investigation will allow the commission to conclude that no special tax treatment or benefits have been granted to Amazon.”

The consortium said the documents it had obtained involved deals negotiated by PricewaterhouseCoopers, an accounting firm, on behalf of hundreds of corporate clients.