(Changes wording in paragraph four to show Almunia said he would not conduct a formal market test, instead of that he would not consult complainants)
SAN FRANCISCO/FRANKFURT, July 22 (Reuters) - European Union antitrust regulators are preparing to step up investigations of Google Inc's practices on several fronts and are likely to revise certain terms of a settlement involving its search engine that was proposed earlier this year, the Wall Street Journal reported on Tuesday.
Google has been the target of a European Commission investigation since November 2010, when more than a dozen complainants, including Microsoft Corp, accused the company of promoting its own services at their expense.
In February, Google agreed to make concessions on how it displays competitors' links, striking a deal that ended a three-year antitrust probe and avoided a hefty fine.
But the agreement has been criticized, both by tech companies and European politicians, as inadequate. Competition Commissioner Joaquin Almunia said at the time he would accept Google's concessions without conducting a formal market test, prompting a furious response.
On Tuesday, the Commission said it was considering formal complaints to the agreement and aimed to make a decision on the matter in September.
"We have written to the formal complainants in the ongoing proceedings and we have not received yet all their replies," a spokesman for the Commission said. "In early August all replies will have been submitted. We will then thoroughly analyze the arguments they contain and, depending on the outcome of that analysis, the next steps will be decided by Mr. Almunia in September."
Google may face other investigations, including regarding its Android operating system for smartphones.
The European Commission recently sent a fresh request for information to handset makers on their dealings with Android, which runs on roughly four-fifths of the world's smartphones. That line of inquiry is likely to turn into a formal investigation, the Journal reporting, citing a person with knowledge of the situation.
Last month, Almunia said he could initiate an investigation of YouTube if he saw any attempt by Google to abuse its dominance of online video searching.
In a guest editorial for German newspaper Bild on Tuesday, Martin Shulz, head of the EU Parliament, argued that the decision on how to treat Google should not be taken by an outgoing Commission. Almunia will vacate his post later this year.
"The EU has to make the decision on how to deal with Google with care," he said in the editorial. "It cannot be that we've been discussing Google for months, and that the decision takes place when half of Europe is on holiday."
Google did not respond to a request for comment. (Reporting by Edwin Chan and Kristina Cooke in San Francisco and Harro ten Wolde in Frankfurt; Editing by Chris Reese and Dan Grebler)