The communications giant admitted 10% of its 22 million customers had suffered an intermittent service since noon yesterday.

It said some phone numbers across the UK were not working, but was not because of the technical fault that had resulted in millions of customers cut off in July 2012.

Initially, O2 promised to have the problem fixed by 4.30pm yesterday but the issue was marked as "on-going" on its network status page more than 60 minutes after that time.

The problems were apparently compounded by the number of people checking with the network to see if their phones were working.