Tax officials in Denmark are reportedly paying an unknown source around £1 million (~$1.3M) for secret financial information on hundreds of Danish nationals.

Their names appear in the Panama Papers, leaked earlier this year, which consist of 11.5 million files from the database of Mossack Fonseca—the world's fourth biggest offshore law firm.

This is the first time, according to Danish newspaper Politiken, that Denmark has agreed to buy information on possible tax evaders in this way. Denmark also seems to be the first country to admit that it's acquiring data from a source with access to the leaked Mossack Fonseca documents. [Update: apparently Iceland made an earlier deal—see comment below.]

Politiken reported that the unusual deal was the result of secret negotiations conducted with an unknown seller. What seems to have clinched it was a "free sample" that was sent to prove the value of the data. An official with Denmark's tax office explained:

This [sample] convinced us of the quality of the documents. They are real and they contain information that is very relevant to us. Both of specific individuals, and especially super interesting knowledge about the methods used by advisers and the middlemen they use. This can give us a breakthrough in the investigation of tax havens.

In return for the payment, the Danish government will apparently receive data from the Panama Papers relating to about 320 cases involving 500 to 600 Danes. The tax authorities expect to have the relevant files at the end of September.

Although Politiken reported that the country's tax minister "discreetly secured the backing of a majority in parliament" to conclude the negotiations, the deal is not without its critics. Another article in the newspaper, written by the national secretary of Denmark's Young Conservatives, asked: "If I bought a set of documents which I knew was stolen, then I would be convicted of receiving stolen goods. Why is it different because the taxman is involved?"

Despite that controversy, Denmark's move might clear the way for other countries to make similar deals. As noted by the Guardian, government officials in Germany paid under €1 million (~$1.1M) for a significantly smaller Mossack Fonseca leak in 2014. Customers of Germany's second largest bank, Commerzbank, were later raided on suspicion of tax evasion.

The lucrative nature of the deal might also encourage others to leak information that could be considered in the public interest. The Greens/EFA group in the European Parliament wants to encourage responsible leaking by bringing in legal protection for whistleblowers, and the organization has published a draft version of its proposed EU whistleblowers Directive.

A German website reported that more than 100 MEPs have signed an open letter supporting the idea of better legal safeguards.