BT has announced the launch of a new internet filter designed to protect children online.
The controls will automatically be set to "on" for new users. Customers who do not want the service will have to actively choose not to turn it on.
The filter is designed to block sites deemed unsuitable for children.
The move comes after the government called for internet service providers to filter legal pornography and other adult subjects "by default".
The BT Parental Controls filter will cover any internet-enabled device connected to its home broadband service.
The implementation of the controls will be pre-selected for new users who are setting up their internet connection for the first time. They will have to confirm this option and then will be asked to set a filter level.
There will be three levels - strict, moderate and light - or customers can choose to turn the filter off.
Existing users of BT's broadband will be contacted during 2014 and asked to make a decision on whether or not they want to set up the new service.
Sites that show pornography, refer to illegal drugs or promote self-harm will all be blocked. Other categories of sites that the filter can be set to block include nudity, social networking and gaming.
Users can also personalise the filters to block access to sex-education sites and search engines.
BT currently has 6.8 million broadband customers.
"BT takes the issue of online child protection extremely seriously and we are very pleased to be able to launch the whole-home filter to help parents keep their families safe online," said BT's managing director of consumer commercial marketing and digital, Pete Oliver.
The National Crime Agency's Child Exploitation and Online Protection Command (CEOP) said it welcomed the move by BT.
The government has said by the end of 2014, 20 million homes - 95% of all homes in Britain with an existing internet connection - will be required to choose whether to switch on a whole-home "family- friendly" internet filter.
Sky and Talk Talk have already implemented their own version of a "family-friendly" filter. Virgin is expected to introduce something similar in the new year.
In November, Google and Microsoft announced that 100,000 search terms that related to illegal material would be blocked by their search engines.