This article is more than 4 years old

This article is more than 4 years old

A former employee of PricewaterhouseCoopers has been convicted of theft by a court in Luxembourg following an unprecedented leak of controversial tax deals granted to many of the world’s largest corporations.

Antoine Deltour received a 12-month suspended sentence and was fined €1,500 (£1,200). Deltour was found guilty on charges including theft and violating Luxembourg’s strict professional secrecy laws.

In 2014, Deltour won widespread praise for helping bring to light hundreds of controversial tax deals granted in previous years by the Luxembourg tax office. The revelations, known as the LuxLeaks, helped lay bare the tax arrangements of companies including Burberry, Pepsi, Ikea, Heinz, Shire Pharmaceuticals and others.

The Guardian and other media outlets, working with the International Consortium of Investigative Journalists, used the leaked data to expose controversial tax practices rubber-stamped by Luxembourg. The documents disclosed that the the country’s authorities had helped 340 big companies to minimise their tax payments, in some cases to 1% or less.

These revelations sparked parliamentary inquiries around the world and helped shape major reforms to the way multinationals are taxed.

But Luxembourg’s finance minster, Pierre Gramegna, described the leak as “the worst attack” his country had ever experienced. During Deltour’s trial, prosecutors claimed the former PwC employee was an “anti-capitalist” and requested he be sentenced to 18 months in prisoon – though they later indicated they would accept a suspended sentence.

PwC also gave evidence at trial, pressing for a conviction. The accountancy firm insisted Deltour was a thief, not a whistleblower. He was accused of costing the company huge sums, though PwC told the court it sought only a symbolic €1 in damages.

In his annual statement last year, the British boss of PwC Luxembourg, John Parkhouse, said: “We all experienced the impact of the document theft, notoriously known as LuxLeaks. It is a real credit to our community in Luxembourg that we have not only weathered the storm, but have emerged as leaders in the international tax debate as well as retaining strong growth across the economy.

“It is truly in difficult times such as these, that we can feel the unique spirit of Luxembourg.”

Outside court, Deltour’s supporters immediately indicated he would appeal. In a statement, the whistleblower said his sentence ignored the public interest. It was, he said, “detrimental to citizen’s information and the good functioning of the democracy”.

His supporters include grassroots activists, dozens of whom protested daily outside the court during his trial, as well as many senior tax reformers and politicians.

Last year, the European competition commissioner, Margrethe Vestager, said: “LuxLeaks could not have happened if it was not for the whistleblower, and the team of investigative journalists. The two worked very well together to change the momentum of the debate about corporate taxation in Europe.

“I think everyone should thank both the whistleblower and the investigative journalists who put a lot of work into this.”

France’s finance minister, Michel Sapin, has also expressed “solidarity” with Deltour, while more than 200,000 people have signed a petition in support of the 30-year-old whistleblower.

Another former PwC employee, Raphael Halet, was convicted on similar charges on Wednesday relating to the theft of a smaller cache of tax deal papers which was also eventually leaked to journalists. He was given a a nine-month suspended sentence and was fined €1,000.

Edouard Perrin, a French journalist accused of helping Halet, was acquitted.