Campaigners are threatening to sue the private security giant G4S over alleged privacy and data protection breaches after it began filming asylum seekers in their own homes without their consent.

Last month, more than 60 G4S housing and welfare officers working on a government contract to house 30,000 asylum seekers were issued with body-worn cameras in a measure designed to tackle violence and threats against staff.

G4S confirmed that the cameras were operated on a “constant recording mode”, including when officers are dealing with asylum seekers and their children in their own homes. G4S claims the initiative has the support of the Home Office, but it has alarmed both the information and surveillance commissioners. The Information Commissioner’s Office has raised concerns with G4S after being alerted by the Guardian.

Asirt, a Birmingham-based advocacy group for asylum seekers, is considering taking legal action against G4S on the grounds that use of the cameras flouts the right to private life in the home under article 8 of the European convention on human rights.

Dave Stamp, the group’s project manager and an immigration lawyer, said: “No legal action has been initiated as yet, though it’s certainly something we will be considering in the absence of appropriate action by G4S in the very near future.

“While it may be lawful to film or record people in public without their consent, these people are not in a public place: they are in their own homes, where they have a reasonable expectation of privacy.”

In a letter to G4S, written on behalf of West Midlands Strategic Migration Partnership, Stamp said: “If statutory guidance suggests that it is not appropriate for parking enforcement officers to be recording members of the public for the entirety of their working day, why is it appropriate for G4S staff perpetually to record interactions with people going about their business in their own homes, potentially wishing to protect their privacy around, for example, sensitive personal relationships?”

Stamp also claims that use of cameras potentially breaches data protection laws because asylum seekers have no practical means of reviewing the footage if requested.

The surveillance camera commissioner, Tony Porter, said he planned to raise concerns with the Home Office, but was powerless to act against G4S as it is not among the bodies he monitors.

Porter said: “I find it surprising that G4S feel the need to record continuously, which runs the risk of breaching article 8 of the ECHR around the right to privacy.”

Porter has been working with the police on how public privacy can be protected as forces roll out body-worn video for frontline officers. He advised the police against operating body-worn cameras in constant recording mode, particularly inside people’s homes.

He said: “In people’s homes there is a greater invasion of privacy. Having it on all the time is not proportionate, and police recognise that.”

Asirt claims G4S has failed to consider the impact of the move on the privacy of asylum seekers and the discomfort it would cause. It said in one instance, a Muslim mother being housed in Stoke felt compelled to put on a headscarf in her own home. She was being filmed by a female G4S officer, but was concerned that a man would view the footage.

The Information Commissioner’s Office pointed out that the Data Protection Act gives people rights around how their personal data is used, including images obtained from body-worn video.

A spokesman said: “That includes considering the justification for using what can be a privacy intrusive approach, and factoring in individuals’ rights to access information held about them.

“Continuous recording will require strong justification, as it is likely to be excessive and cause a great deal of intrusion.”

G4S has insisted that a privacy impact assessment was conducted before the cameras were issued, but it has refused to make it public.

Under a code of practice produced by the information commissioner, individuals have a right to review footage within 40 days of requesting it. G4S insists that asylum seekers will be able to review footage if requested, but it has given contradictory statements about how long the footage will be retained.

In a letter sent last month to asylum seekers [pdf] it said “footage will be deleted each day, unless there has been an incident”. But in an accompanying Q&A [pdf] it said “all footage will be stored for no more than six months before being deleted”.

A spokesman for G4S explained that each camera has a 30-hour memory before it begins to overwrite. As a result, footagewill be available to review for up to only 10 days.

The company said it felt it was necessary to issue the cameras after recording 73 incidents of assault or threatening behaviour against its officers in 2016.

John Whitwam, the head of G4S immigration and borders, said: “Our considered view after looking at the evidence is that these devices will help to reduce the incidents of intimidation and violence experienced by our staff who typically work alone, as well as afford protection to service users by providing an impartial source of evidence when we investigate complaints against our team.

“Body-worn cameras have been shown by numerous agencies to afford protection and accountability, which is of importance not only to our staff but also to those vulnerable people to whom we provide a critical service.”