Father of two teenagers, Seamus Kelly, was surprised to find out the cafe he visits in Cheap Barbour Jackets Manchester's Northern Quarter has unrestricted internet access.

He told Sky News "I think in some ways the biggest issue is not knowing what they're looking at.

"If it's at home you might have a certain amount of control over the system but when it's out not only do you not have control but you've also got absolutely no idea what they may or may not be coming across and it is quite worrying."

Outside a cafe in south Manchester a group of 15 and 16 year olds told Sky News they have all had smartphones from the age of 13 and frequently use Wi-Fi to go online.

They admitted they know people who use sites their parents would not allow them access to.

Earlier this year David Cameron backed a campaign by children's charities calling for a ban on adult content on all public Wi-Fi.

John Carr is among the world's leading authorities on children's and young people's use of the internet.

He told Sky News: "Virgin, O2 and Sky already block access to adult content and the other major Wi-Fi providers in the UK - BT, Arqiva and Nomad - have announced their intention to do the same by the end of this year.

"There is also some talk about developing a 'kitemark' to allow shops, hotels, Barbour Waxed Womens trains, buses that provide Wi-Fi access to confirm that they provide a filtered service."