There is "no realistic prospect" of the government meeting its own deadline to install smart meters, according to the National Audit Office (NAO).
The public accounts watchdog has joined a chorus of voices - including a group of MPs and Citizens Advice - which say the target is impossible to reach.
Every home in Britain is supposed to have a smart meter - which avoids the need for customer readings - by 2020.
However the government has insisted that it will meet its commitment.
The NAO also said that nearly one million smart meters are no longer working properly, and that the coldest parts of Britain have the fewest meters.
'Deadline requires 30 meters a minute' Deadine 'should be extended'
To meet the deadline, installers will need to replace 39 million old meters within the next two years, according to the NAO.
In comparison, just 12 million meters have been replaced over the last six years.
Earlier this week the consumer group Which? said that the industry would need to install 30 meters every minute over the next two years to meet the target.