Britons who want to watch free porn online may have to prove their age using their passport in as little as eight weeks.

In a move intended to help prevent children accessing inappropriate material online, UK websites which comprise of more than one third pornographic material will have to age-check their users.

Even free-to-access sites will be locked down behind a non-pornographic landing page and many of the country's most popular sites have signed up to the AgeID system, which requires users to verify their age via an official form of ID such as a driver's license or passport.

The start date of the scheme, introduced in the 2017 Digital Economy Act, has been put back several times but is scheduled to come into force in April 2019.

The new law is set to come into effect from April and users will have to prove their age to browse porn

Free porn websites including pornhub and youporn have signed up to the scheme

AgeID spokesman James Clark explained to The Metro: 'When a user first visits a site protected by AgeID, a landing page will appear with a prompt for the user to verify their age before they can access the site.'

'Each website will create their own non-pornographic landing page for this purpose.'

When someone first clicks on a site, they'll be asked to register with AgeID and verify their age using a Mobile SMS, credit card, passport, or driving licence.

Users will then be able to use their AgeID username or password to access all porn sites that use AgeID – though some may use different age verification systems.

Clark said: 'It is a one-time verification, with a simple single sign-on for future access. If a user verifies on one AgeID protected site, they will not need to perform this verification again on any other site carrying AgeID.'

The AgeID network will allow users who have provided their passport, driving licence, or other form of ID, to access multiple sites which use the same verification app

Those who don't want to use the AgeID system will be able to access porn sites using a voucher available in high street shops, which users can link to an app known as Portes.

Through Portes, they can then login to sites without having to hand over their email address.

Mr Clark said: 'The PortesCard is available to purchase from selected high street retailers and any of the UK's 29,000 PayPoint outlets as a voucher.

The new law is intended to prevent youngster accessing inappropriate material

'Once a card or voucher is purchased, its unique validation code must be activated via the Portes app within 24 hours before expiring.

'Once the user has been verified, they will automatically be granted access to all sites using AgeID.'

Each PortesCard will cost £4.99 for use on a single device, or £8.99 for use across multiple devices.

Sites face fines of up to £250,000 or a blanket block by UK internet service providers if they do not comply with the rules.

Regulators will be also able to block porn websites if they fail to show that they are denying access to under-18s.