An extra 500,000 homes and businesses will get automatic warnings about future flooding after the Environment Agency signed them up to its free service.
The latest move will bring the total number of registered properties for the Floodline Direct Warnings service to just below one million, as almost that number have already signed up for the scheme voluntarily.
Anyone renting or owning a property considered to be at risk from river or sea flooding will now have to opt out if they do not want to receive a warning call to their landline phone after the end of February.
Heavy flooding in summer 2007 devastated the infrastructure in parts of Yorkshire, the West Country and the Midlands, and the subsequent Pitt Review recommended rolling out the Floodline service across England and Wales.
Environment Agency chairman Lord Chris Smith said as many as one in six homes were at risk of flooding.
"By automatically signing up an extra 500,000 homes and businesses, we will more than double the number on our system to almost one million, giving more people vital time to get prepared for flooding, and by doing so, protecting lives and property," he said.
© Press Association 2010