A British spyware manufacturer is facing legal action from Bahraini dissidents over allegations it sold products to Bahrain knowing they would be used to crack down on protests during the Arab spring.

Gamma Group sold the Bahraini government its “FinFisher” software, which infects and spies on a target computer, despite numerous press and NGO reports about human rights crimes in the country, according to a letter of claim sent to the company last week.

A lawyer for Gamma said that no evidence of the company’s participation in human rights abuse had ever been produced and that the claim would be defended.

The claimants in the case – Hassan Mushaima, Ali Mushaima, Moosa Mohamed and Saeed Shehabi – are being represented by the law firm Leigh Day. They are suing Gamma and related companies in the UK and Germany, as well as the company’s owner, Louthean Nelson, as alleged accessories in the misuse of private information by the government of Bahrain.

Gamma, which was founded in the 1990s, is a manufacturer and distributor of spyware, software designed to covertly monitor communications. Its principal product is the spyware suite called “FinFisher” that covertly harvests call and email data from target devices.

Promotional material published by WikiLeaks in 2011 details how the software can bypass common antivirus systems, log the keystrokes of target computers, and activate a device’s microphone or camera for “live surveillance”.

The claim alleges that the four claimants’ computers were targeted with the FinSpy program, which was manufactured in the UK and sold to the Bahraini government. Gamma is accused of also providing training to Bahraini government officials on how to correctly use the software, along with technical support and software updates.

The claimants say they were targeted by the government of Bahrain in retaliation for their pro-democracy campaigning during the Arab spring. Hassan Mushaima, the first claimant and secretary general of the opposition Haq Movement, was jailed for life in 2011 by a military court. His son Ali is the second claimant.

All four allege that the Bahraini government attacked their computers while they were in the UK. One, Shehabi, is a British citizen.

There were popular uprisings in Bahrain, a hereditary monarchy, in support of democratic reform in 2011. The Bahraini government ultimately suppressed the protests with military force, supported by Saudi Arabia.

In 2012 Gamma claimed to Bloomberg that it had never sold FinFisher software to Bahrain, and a company executive speculated that the Bahraini government was using a demonstration copy that had been stolen and used without permission.

However in 2014 WikiLeaks published data, apparently hacked from Gamma’s servers, which included sales records and logs detailing communications between Gamma and the Bahraini government.

According to the letter of claim, the logs indicate that between 2011 and 2012 the government contacted Gamma with detailed requests for technical support for FinSpy products on at least five occasions. One of the communications included a list of 77 targets, including the four claimants.

Gamma insists that it only sells its products to governments and law enforcement agencies, but has consistently refused to identify its clients. However, researchers at CitizenLab in Toronto, Canada claim to have identified FinFisher command and control servers in at least 35 different countries, including Kazakhstan, Turkmenistan and Venezuela.

Nelson, a 57-year-old British national who reportedly lives in Beirut, Lebanon, has worked in intelligence for more than 20 years, according to the trade publication Intelligence Online.

In February 2013 the campaigning group Privacy International filed a complaint with the British government alleging that Gamma had violated OECD guidelines on responsible business conduct.

Two years later the government concluded that the guidelines had been breached. However there are no penalties for breaches, and the following year the government said Gamma never responded to its report.

A spokesperson for Leigh Day said: “Human rights defenders all over the world live under the threat of constant surveillance because of the technology produced and sold by companies such as Gamma. This threat of surveillance has the effect of chilling activism and significantly contributes to a climate of repression.

“This case will hopefully shed light on a very secretive industry and hold to account those who sell spyware to repressive governments.”

Peter Lloyd, a solicitor representing Gamma Group, said: “The matters raised by Leigh Day in its letter of claim have been exhaustively explored in other forums. No evidence has ever been produced of any part of the Gamma Group participating in any human rights abuse by the government of Bahrain. The claim is fundamentally misconceived and will be defended.”