EU regulators will press Google for more concessions to end a three-year investigation into claims it squeezed out web rivals.
Competition Commissioner Joaquin Almunia, acknowledging critics who say the response from the world's most popular search engine is inadequate, said Google would almost certainly be asked to improve its proposals.
Last month, Google offered to label its own products in internet search results and make it easier for advertisers to move to rival platforms.
The offer came after more than a dozen firms including Microsoft accused Google of squeezing them out, prompting the EU competition watchdog to open an investigation.
Rivals, including British price comparison price site Foundem and German online mapping company Hotmaps, say Google's proposals would force them to compete among themselves, raise their costs and increase merchants' dependency on Google.
Lobbying group and complainant ICOMP, which counts Microsoft and four other rivals among its members, doubt that Google could allay anti-competitive concerns with fresh concessions.
"The current package is clearly insufficient. It is really unlikely if the current proposal can be improved to such a point where it can be effective," says ICOMP's lawyer David Wood.
The EU competition authority initially gave complainants until May 26 to comment, but later extended the deadline to June 27 following pressure from the companies.
"After, we will analyse the responses we have received... almost 100 per cent we will ask Google: you should improve your proposals," Almunia told lawmakers during a hearing at the European Parliament yesterday.
Google spokesman Al Verney said the company would continue to work with the Commission to settle the case. A settlement would mean no infringement finding or fine, which could be as much as $5bn for the company in such a case.
Almunia also said he had yet to decide whether to open a formal investigation into Google's Android operating system, widely used in smartphones phones and tablets.
"We have received a formal complaint regarding some aspects of the Android ecosystem. We are working on it, we have not decided if we will open or not a formal investigation," he said.
Last month, a group of companies including Microsoft and Nokia filed a complaint with the Commission, accusing Google of blocking competition in mobile telephony.
Android-powered devices have a 60 per cent share of the global smartphone market versus Apple's 19 per cent, according to consultancy Canalys.