Full advertising regulations are to be extended to retailers' own websites and online areas like Twitter and Facebook, it was announced today.

The online extension has "the protection of children and consumers at its heart" and will come into effect in March next year, the Advertising Standards Authority (ASA) said.

The ASA's current remit online includes ads in paid-for space and sales promotions wherever they appear.

But from next year the rules covering misleading advertising, social responsibility and the protection of children will apply in full to all online marketing by all sectors, businesses and organisations, regardless of size.

The Committee of Advertising Practice (CAP), the body responsible for writing the regulations, said it had decided to extend the ASA's powers in response to a formal recommendation from a wide cross-section of UK industry.

The rules will apply to retailers' websites and ads placed in online areas that are free of charge, such as social networking sites like Facebook and Twitter.

However, in an effort to protect freedom of speech online, the rules will focus on ads that sell products rather than journalistic and editorial content, the ASA said.

The ASA will have the ability to demand the removal of paid-for links to pages hosting a banned ad, with the agreement of search engines.

It could also place its own advertisements online highlighting an advertiser's continued refusal to comply with a ruling.

The ASA urged website owners and agencies to become familiar with the new rules ahead of the March 1 deadline.

ASA chairman Lord Chris Smith said: "This significant extension of the ASA's remit has the protection of children and consumers at its heart.

"We have received more than 4,500 complaints since 2008 about marketing communications on websites that we couldn't deal with, but from 1 March anyone who has a concern about a marketing communication online will be able to turn to the ASA."

CAP chairman Andrew Brown said: "Extending the online remit of the ASA has been a top priority for UK industry over the last couple of years.

"Our aim has been to extend further in the online world the principles that are already well established in our system, namely those of effective consumer protection and fair competition."