Retailers must carry out expensive upgrades of their alarm systems by 1 April - or face being blacklisted by police.

They now have just over two months to install the expensive new audio verification technology police believe is needed to reduce the number of false alarms caused by staff pushing panic buttons for the 'wrong' reason such as antisocial behaviour outside stores.

However, with upgrades expected to cost £2,000 on average and take up to three months, experts are warning that many retailers will not have the new systems in place by the deadline.

The new policy follows a survey by security specialist SSS last year that found 98% of store alarms had been falsely triggered at some point.

Under the policy, the Association of Chief Police Officers is demanding alerts be verified via an alarm-receiving centre before police are sent. Audio verification alarms incorporate listening devices so emergency call centre operators can listen in once an alarm has been triggered to assess if police are really needed.

The Co-operative Group and Carphone Warehouse have been running a trial of the new verification technology in conjunction with Acpo and SSS. The trial has reduced false alarms by 96%, saving 246 hours in police time, they claimed. "Staff have welcomed it because it shows the business is doing its best to look after staff and staff safety," said Richard Quinn, national operations manager at the Co-op, which has now begun a programme to update all its systems.

At present two false alarms will result in the automatic police response being withdrawn for three months. From April, retailers will have to prove they have the verification technology in place to get off the blacklist.

The BRC said it accepted verification on alarm calls was necessary. "The level of false alarms is too high and it is not in anyone's interest to see police repeatedly called out unnecessarily," said a spokesman.