Plans to test a mobile phone emergency siren could bring chaos to the roads with drivers panicking upon hearing the piercing alert, ministers have been warned.

The loud, 10-second blast will be sent to all mobiles on Sunday, April 23 as part of a nationwide test of the system announced last month by Oliver Dowden, the Cabinet Office minister.

However, officials are concerned that the potential consequences have not been fully thought through. Discussions have taken place with the transport sector, domestic violence charities and sporting officials as well as the police, fire and ambulance services about the trial.

Officials have met with the RAC to discuss how any risk to drivers can be reduced to avoid car crashes. 

Road safety campaigners have warned that the siren could distract drivers caught unawares.

Edmund King, president of the AA, welcomed the scheme, but questioned how wise it was to test it on a day “Sunday drivers” - often less experienced motorists - take to the roads.

“If they have the phone in the car and an odd sound goes off there could be some form of panic,” he said.

“Even if they have a hands-free system the odd sound could mean they reach for the phone. So, there’s no doubt that there’s a threat of distraction for some drivers.”

Motorway signs will also be used in the run-up to the test to warn drivers not to check or use their phones.

Ministers have also approved a major publicity campaign to advise the public about the siren.

Campaigners representing victims of domestic violence are understood to have “shared concerns” with the Government that women could also be put at risk by the trial.

Some domestic abuse victims have “lifeline” phones, which are devices kept secret from a violent partner, but the siren could uncover these devices if they are not programmed to reject the test.

Following talks with the Football Association, officials have chosen not to send the alert during the televised FA Cup semi-final between Manchester United and Brighton at 4.30pm.

However, fans watching other matches could be affected and will be “informed and supported” to avoid panic in stadiums, a well-placed source said.

The Telegraph understands the Cabinet Office will instruct local authorities to inform residents and ask the BBC to mention it in television and radio bulletins.

The alert will disable users’ phones leaving a "welcome message" on screen until they acknowledge it by clicking on an “OK”  message.

It is illegal to hold and use a mobile phone while driving, and those caught doing so can be given six penalty points and a £200 fine.

'Minimal' risk to the public

It is understood ministers believe the “minimal” risk to the public by testing the system is outweighed by the benefits of having a scheme that can warn of emergencies such as floods, wildfires and terror attacks. Similar systems are used in other European countries and the United States.

Emma Pickering, of the Refuge charity which supports women and children experiencing domestic abuse, said it had been in contact with the Government about the test.

“Our concerns are centred on the very real risk to survivors of domestic abuse who may have secret or secondary phones hidden within the home, which they must ensure are not discovered by their perpetrators. These devices can be a lifeline for women who need to access support or flee their abuser.”

Refuge has recorded two videos explaining how women can opt out of the service on their device.

Lucy Hadley, head of policy at Women's Aid, said it was urging ministers to “ensure the safety of domestic abuse survivors is central to the roll-out of the scheme”.

She added: “The Emergency Alerts pose a risk, not only because an abuser could discover a survivors’ second phone, but also because they could use this as a reason to escalate abuse.”

'Effective communications' essential

Caroline Abrahams, director at Age UK, welcomed the alert system but wanted “effective communications… so older people know what to expect, and that there’s no need for concern.”

A government spokesman said: "Emergency Alerts transform our ability to warn and inform people who are in immediate danger - making sure an urgent message can be sent to mobile phones in a specific area when there is a risk to life.

"At every stage of the process we have worked with our emergency services, transport, charities, and vulnerable groups, to make sure people are aware of the service, and those who wish to opt out are able to do so."

The Telegraph understands that the UK’s system can only be activated with the permission of Mr Dowden, the Chancellor of the Duchy of Lancaster.

The Emergency Alert system is designed to send messages to an area as specific as one council ward.

The Government does not identify users it wishes to alert but tells mobile service providers where it should be sent.

In 2018 in Hawaii, an alert sent accidentally sparked terror because it warned of an inbound missile strike. A second message explaining the error was not sent for a further 38 minutes. By Tony Diver, Telegraph