A leading British arms company has been selling spy software across the Middle East, potentially risking the security of activists and dissident groups.

The findings come after a year-long investigation by BBC Arabic and a Danish newspaper, which revealed that BAE Systems had been selling a mass surveillance software called Evident, acquired after the purchase of Danish company ETI in 2011, to governments in the Middle East, including those involved in crackdowns on pro-democracy activists.

"You'd be able to intercept any internet traffic," said a former ETI employee speaking anonymously to the BBC.

"If you wanted to do a whole country, you could. You could pin-point people's location based on cellular data. You could follow people around. They were quite far ahead with voice recognition. They were capable of decrypting stuff as well."

If you wanted to do a whole country, you could. You could follow people around. They were quite far ahead with voice recognition - Former ETI employee

Among the clients for the software was the government of the former Tunisian president, Zine El Abidine Ben Ali, who used it on opponents before being overthrown in the 2011 Arab Spring demonstrations.

"ETI installed it and engineers came for training sessions," explained a former Tunisian intelligence official, speaking to the BBC.

"[It] works with keywords. You put in an opponent's name and you will see all the sites, blogs, social networks related to that user."

According to Freedom of Information requests made by the BBC and the Dagbladet Information newspaper in Denmark, other clients included Saudi Arabia, the UAE, Qatar, Oman, Morocco and Algeria.

The rise in surveillance technology in the Middle East is thought to have had a serious impact on the activities of pro-democracy campaigners in the region since the beginning of anti-government protests in 2011.

Yahya Assiri, a former Saudi air force officer who fled the country following the posting of pro-democracy comments on social media, told the BBC he "wouldn't be exaggerating if I said more than 90 percent of the most active campaigners in 2011 have now vanished."

Marietje Schaake, a Dutch member of the European Parliament, described the sale of the technology as "unacceptable".

"Each and every case where someone is silenced or ends up in prison with the help of EU-made technologies I think is unacceptable," she told the BBC.

"The fact that these companies are commercial players, developing these highly sophisticated technologies... requires us to look again at what kind of restrictions maybe be needed, what kind of transparency and accountability is needed in this market before it turns against our own interest and our own principles."

The UK government has, however, been keen to support BAE Systems, a major employer, with regards to its activities in the Middle East.

In particular, Saudi Arabia is a vital market for the company, which employs more than 80,000 staff worldwide and accounts for one percent of UK exports, according to the company.

The UK government has approved more than $4.2bn of arms to Saudi since the start of the conflict in Yemen 2015, and last month The Times reported that the British government threw its weight behind the company to secure a long-awaited Typhoon jet contract with Saudi Arabia for 48 new aircrafts.

Olly Sprague, Amnesty UK's programme director for military, security and police, told MEE that BAE is hiding behind the UK's "warped rules on arms exports”.

“BAE Systems acknowledge they have more than 6,000 people working in Saudi Arabia helping to strengthen the country's arms capability – so it is outrageous that they continue to hide behind the UK Government's warped 'rules' on arms exports as a justification for their work,” he said.

The UK Department for International Trade issued the following statement: "The government takes its defence export responsibilities very seriously and operates one of the most robust export control regimes in the world.

"All export licence applications are assessed on a case-by-case basis against strict criteria, taking account of all relevant factors at the time of the application, including human rights considerations."