Mark Evans, the CEO of Telefonica (O2) said: "I want to let our customers know how sorry I am for the impact our network data issue has had on them, and reassure them that our teams, together with Ericsson, are doing everything we can".
It said most of the affected customers' network services have been successfully restored during the course of the day, and it was working closely with the remaining customers still experiencing issues.
It is unclear whether the O2 outage, said to be the result of a "global software issue", is linked to the problems with Angus Council's parking meters.
'A statement reads: "The network issue we are now experiencing remains a top priority for us and we are working as quickly as possible to fix the issues".
This means that the number of impacted customers is, in reality, likely to be much higher than 25 million.
One said: "My mobile network has been down all morning so far".
O2's data network has gone down, leaving users unable to access the internet..
O2, Britain's second biggest network, and Japan's Softbank (9984.T) reported network outages on Thursday, leaving many customers unable to access internet services.
It was thought that over a staggering 32 million O2, Giffgaff and Lycamobile customers were left without service.
It has confirmed engineers are working to fix the issue.
"One of our 3rd party suppliers has identified a software issue in their system".
"We will continue to work with Ericsson through the night, who have assured us that a full service will be restored for customers by the morning".
"We'd encourage you to use Wi-Fi wherever you can and we are really sorry".
The Sky Help team, responding to customer concerns on Twitter, say the problem has been pinpointed and staff are working with O2 to resolve the situation.