The Citizencard service, developed by consumer credit services company Experian, uses information provided on an application form and details on public databases to verify the age and identity of applicants.
The Interactive Age Check (iAC) scheme, will enable accredited websites to check the details of users before allowing them access to the site.
All accredited sites will display the iAC logo and will be subject to "mystery user" tests. Three failed tests will result in the naming and shaming of the site and the withdrawal of accreditation.
The scheme will open up new opportunities for e-commerce sites in areas such as gambling, financial services, videos and alcohol, because they will be able to trade with adults that do not possess credit cards, confident that they are not under-age, Experian said.
The company estimates that 35% of UK consumers over the age of 18 do not own a credit card.
"The online authentication tools will enable many more internet transactions with consumers without credit cards while providing a sure guarantee of age and identity when selling age-restricted products and services over the internet," said Richard Fiddis, chief operations officer at Experian.
Hilary Benn, the Home Office minister responsible for online child safety, said, "We support all steps to assist in providing online authentication, which provides protection for consumers and peace of mind for parents."