London - Google is promising businesses greater returns on advertising if they sign up to its social network, in a fresh bid to take on rivals Facebook and Twitter.

The internet search giant has been emailing advertisers boasting that businesses with Google+ pages see a 5-10 percent rise in click-throughs when linked with its AdWord campaigns. These display adverts on Google when users search for specific words.

Google also features businesses' Google+ pages prominently on the right hand side of search results. These also show recent posts on the page and the number of people who have given a “+1” - the equivalent of Facebook's “like” button - to those brands.

Insiders suspect the push by executive chairman Eric Schmidt to sign up companies to the social network, launched in November 2011, is a response to innovations from Twitter and Facebook.

Twitter last week introduced a system allowing businesses to tailor advertising campaigns on the microblogging site and Facebook last month unveiled Graph Search, a feature allowing users to search all the connections across the site.

Having more businesses on Google+ could strengthen the company's commercial clout as it would allow it to build up more detailed pictures of the brands and businesses users like through the +1 feature.

But one advertiser accused Google of “hacking its own system” to ensure the social network's success. When users search on the site, those brands or businesses on the social network are given greater presence, raising questions over whether Google is abusing its power.

It sparked a similar controversy last September when it launched its own car insurance comparison site. Google is also talking to music labels about launching a streaming service, so it is less reliant on advertising. - The Independent on Sunday