Google has refreshed its range of advertising formats in an apparent attempt to further cement its lead in the online ad space.

The search giant's domination of the market has been questioned recently, particularly by Rupert Murdoch who is reportedly considering delisting News Corporation titles from Google's index and striking an exclusive deal with Microsoft's Bing search engine.

The new Google formats add features to interactive online ads, such as allowing web shoppers to check inventory and availability on a particular item at an online store.

Other features offer the ability to place an ad for all retail locations in a particular area, for example a chain of restaurants, and comparison ads that let shoppers compare items side by side in the same window.

Google has been trialling the new formats in the US in recent weeks and has now rolled them out officially.

Susan Wojcicki, vice president for product management at Google, claimed that the new formats will offer advertisers more informative ads with better features, and improve the online shopping experience for consumers.

"While we experiment with new formats, we'll remain loyal to our core principle: that getting the right ad to the right person at the right time matters. We're committed to giving you the information you want, regardless of the form in which it might appear," she said in a blog posting.

"Text is often useful, but sometimes videos and pictures are a more effective way to receive information. It also makes sense to provide richer types of information in the ads. If you're looking to buy your mom a new handbag for the holidays, for instance, you might want to see pictures, prices, the addresses of boutiques in your area and a map of how to get there - all within the ad."