The ASA currently has the authority to regulate paid for online advertising, such as banner ads, popup ads and paid search. It will now also be able to regulate non-paid marketing online.
All UK based company websites, regardless of sector or the size of the company, will be governed by the UK Code of Non-broadcast Advertising, which includes rules to prevent advertisements that mislead, harm or offend.
Since 2008 the ASA has received more than 4,500 complaints about non-paid-for marketing on the internet. The expansion of its remit was agreed following a recommendation from the UK ad industry.
A spokesman for the ASA said the changes will not only be "good news" for consumers, but also be "good for business" as trusted marketing communications are more likely to work and deliver value.
The ASA can enforce sanctions against companies that are in breech of the rules, including naming and shaming the company, removing any paid-for search advertising that links to the offending website, or buying search advertising that highlights the advertiser's non-compliance.
An independent government commissioned review into the sexualisation of young people, published last February, supported industry calls to change the ASA's remit to include commercial websites.
The report noted that increasingly, media messages are being delivered via the internet, with companies spending millions on developing interactive advertisements on their commercial websites.