Operators argue that the current copper-wire network needs to be replaced because it is increasingly unreliable and becoming difficult to maintain. But critics fear the impact on older and vulnerable people, as analogue phone lines still work during power cuts.

Silver Voices director Dennis Reed said: “It is grossly insulting that our petition and letter calling for the deadline to be extended has not even been answered, showing contempt for the hundreds of thousands of vulnerable customers who depend on their landlines for alarm systems and to make emergency calls.

“The Government has its head in the sand over this whole transition process, trusting the telecoms industry to get the job done with as few personal tragedies as possible. What a way to run a whelk stall.

“It is not too late for Andy Burnham to intervene and extend the switchover timetable until 2030 so that the health and safety needs of vulnerable pensioners, disabled customers, and those in remote communities can be properly addressed.”

It comes as the Government’s Be Ready campaign, which urges the public to stockpile supplies in the event of a crisis, also advises people who have not yet “migrated to a modern digital network” to contact their landline provider.

It says: “If you are a vulnerable customer, for example, if you are a telecare user, your communication provider must provide a free backโ€‘up battery unit.”

The Department for Science, Innovation and Technology and Ofcom have been contacted for comment.