Google has been given until July to defend itself in the European Commission's antitrust investigation. The probe was instigated by complaints that Google uses its power in web search to promote its own products over those of competitors.

"By early July, I expect to receive from Google concrete signs of their willingness to explore this route," said European Commission vice-president and competition commissioner Joaquin Almunia at a press conference in Switzerland.

If Google fails to cooperate in time for the deadline, the company will be hit with an official "statement of objections" that could be followed by a fine of up to 10 per cent of its global revenues, which were $37.9 billion (£24 billion) last year. That means Google could expect to face an antitrust fine of up to $4 billion (£2.4 billion).

The search giant has consistently defended itself against accusations that it intentionally manipulates search results to give its own products higher rankings.

In a 7 June op-ed for the Wall Street Journal, CEO of price comparison site Nextag Jeffrey Katz accused Google of being a "brand killer," writing that the company has aimed to "monopolize every avenue through which a company can reach users online."

Google objected in a blog post penned by senior vice-president of engineering Amit Singhal. "It's understandable that every website believes that it is the best, and wants to rank at the top of Google results. The great thing about the openness of the Internet is that if users don't find our results relevant and useful, they can easily navigate to Nextag, Amazon, Yelp, Bing or any other website," Singhal wrote.

No word yet on how Google will formally respond to the European Commission's deadline, but the company seems intent on rejecting antitrust accusations.