Business Secretary Sajid Javid has urged phone provider O2 to 'sort it out' after a flood of complaints from people who had lost the signal on their mobile telephones.

%image(14944117, type="article-full", alt="File photo dated 05/01/15 of Business Secretary Sajid Javid, who has urged phone provider O2 to "sort it out" after a flood of complaints from people who had lost the signal on their mobile telephones. PRESS ASSOCIATION Photo. Issue date: Tuesday May 26, 2015. He tweeted "No signal @O2. Please sort it out" as annoyed customers went online to claim they have had no service for up to five hours. See PA story TECHNOLOGY O2. Photo credit should read: Anthony Devlin/PA Wire")

He tweeted 'No signal @O2. Please sort it out' as annoyed customers went online to claim they have had no service for up to five hours.

People in Manchester, Bristol, Birmingham, Glasgow and parts of Northern Ireland and London have reported problems.

The phone provider, which had suggested that people reboot their handsets and turn their phones on and off again, said there were aware of 'some issues' and 'isolated instances'.

In a series of tweets O2 told customers: 'We're working flat out (and upright too) to get these fixed. Sorry for the problems' and 'Sorry for all the effort you've had to put in Ems. We're making sure our engineers put in even more to fix the problems!'

O2 also insisted that 'our engineers are beavering away and working to fix ASAP.'