No 10 says there are anti-spam measures and people who want to sign a petition have to give an e-mail address and a UK address including postcode, or an overseas address.

BBC: NEWS | UK | UK Politics | Hunting support tops e-petitions

It said the findings should be used to address a postcode lottery in alcohol counselling and treatment services across England.

BBC: Northerners 'are heaviest drinkers'

In addition, postcode entry is more flexible and the app can find locations from the phone address book more reliably.

ENGADGET: TomTom updates its Android app to make it, you know, work