SINGAPORE - By the end of next year, Internet service providers (ISPs) must offer free trials of Internet filtering tools that block out objectionable websites to their broadband and mobile subscribers.

The one-time free trial offer will last for six months or half the term of subscribers' contracts, whichever is shorter, according to a new regulation announced on Tuesday by the Media Development Authority (MDA). After that, ISPs must get subscribers' consent before charging them.

The new requirement is part of the media regulator's plan to improve parental controls as the popularity of mobile devices gives the young easier and quick access to dubious websites. Also, MDA does not want cost to become a deterrent to parents.

The rule comes after a four week-long public consultation from April to May last year. ISPs typically charge $2 to $5 a month for such a service.

"The duration of the free trial period should give parents enough time to try out and assess the usefulness of the Internet parental controls," said MDA, which had earlier proposed a free basic service instead of a free trial.

The decision to go with a free trial would allow ISPs to offer more comprehensive functions - such as monthly reports on the websites visited - to better meet the needs of parents, the authority said.