If you send an alert to millions of phones this weekend, you risk panic, activists warned tonight.
In the UK’s test of the official emergency alarm system, smartphones and tablets will sound a siren-like sound and vibrate for ten seconds at 3pm on Sunday. It activates even when the device is in silent mode.
A message will also appear on a mobile phone’s home screen explaining that the alert is a test. It disappears when the user clicks on it or swipes away.
But motorists warned drivers could become distracted or risk breaking the law by clearing the home screen behind the wheel.
And women’s charities fear the warning could tip off abusers about hidden “lifeline” phones secretly used by victims of domestic violence.
In the UK’s test of the official emergency alarm system, smartphones and tablets will sound a siren-like sound and vibrate for ten seconds at 3pm on Sunday.

Campaigners have wondered why governments would want to warn the public with a loud noise on a quiet Sunday afternoon. (file image)
It is also feared that retirees could be ‘confused or concerned’ if their device goes off without warning.
Andrew Allison of the Freedom Association, a campaign group, said: ‘If governments want to warn us, I’m not sure the best way to do it is to ping everyone’s cell phone with a loud noise on a quiet afternoon.
“I’m always afraid of too much government influence in our lives, and this could be an example of that.”
A senior Conservative politician added: ‘We want a society that is less intrusive, rather than more intrusive.
“Of course, it’s quite possible that this would raise the alarm among people who didn’t know it was coming. It seems very dubious to me and the best I can say about it is that it is strange to disturb people’s Sunday afternoons in this way.’
Green’s colleague Baroness Jones said, “It’s a crazy idea.”
The alert can only be avoided if a phone is turned off or if the user has manually opted out of receiving. Refuge, a domestic violence charity, is so concerned about the potential impact on victims that it has put together a step-by-step guide to turning off the alert.
Spokesperson Emma Pickering said: ‘Our concerns focus on the very real risk to domestic violence survivors who may have secret or secondary phones hidden in the home, which they must ensure is not discovered by their perpetrators.

Automotive groups warned drivers could be distracted or risk breaking the law by clearing the home screen behind the wheel

Refuge, a domestic violence charity, is so concerned about the potential impact on victims that it’s put together a step-by-step guide to turning off the warning
“These devices can be a lifeline for women who need help or need to flee their abuser.”
Lucy Hadley, from Women’s Aid, a domestic violence helpline, said: ‘We work with our members and use our direct services to ensure survivors we come into contact with are informed and know how to opt out.
“We urge the government to ensure that survivors’ safety is at the heart of the roll-out of this scheme, particularly by raising awareness of how to opt-out.”
Caroline Abrahams of the Age UK charity said there were ‘very good reasons’ to test the alarm, but called on the government to ‘step up’ its communications campaign so that ‘no one is surprised’.
She added: “It’s very important that we all know what to expect, especially those older people who might be confused or worried if their phone rings unexpectedly on a Sunday afternoon.”
The AA has questioned whether it was right to test the system on a day when less confident ‘Sunday drivers’ were on the road, warning that the loud siren going off inside a car could cause ‘some sort of panic’.
Government officials decided not to send the warning during the FA Cup semi-final between Manchester United and Brighton which started at 4.30pm. However, other competitions – and the London Marathon – could be affected.
There are even fears that the warning could disrupt matinee performances in theatres. West End players will be urged to turn off their phones.
Similar systems are used for alerts in other countries, including the US, Canada and Japan. In 2018, a mistake led residents of Hawaii to receive a warning that there was a “ballistic missile threat” and conclude “this is not a drill.”
The message that appears on phones reads: ‘This is a test of Emergency Alerts, a new UK government service that will alert you if there is a life-threatening emergency nearby. In a real emergency, follow the instructions in the alert to protect yourself and others. Visit gov.uk/alerts for more information. This is a test. You don’t need to take any action.’
The government said it would use the alarm sparingly and warn primarily about chemical leaks or when severe weather, such as extreme flooding, would be life-threatening.
Chris Phillips of the International Protect and Prepare Security Office said: ‘I see the point in saying to stay away from a certain area in the event of something like a terrorist attack.
‘In that case, a silent message – without an alarm – might be appropriate. But there is a danger in this being overused. I hope this is used wisely.’
Tim Holman, CEO of cybersecurity firm 2-Sec, said: “I’m a little worried about anyone driving a vehicle being momentarily distracted by a smartphone in siren mode. It’s very loud. It’s supposed to be like this.’
The warning system is costing the taxpayer £22 million.
Oliver Dowden, the minister overseeing the plan, said: ‘Getting this system up and running gives us an essential tool to keep the public safe in life-threatening emergencies. It may be the sound that saves your life.’
Tests have been carried out in Reading and East Suffolk. About one in 20 participants subsequently dropped out.