Microsoft stepped up its criticism of Google on antitrust grounds Wednesday, claiming the Internet giant refuses to allow Windows Phone users "proper access" to the YouTube video service.

"Despite government scrutiny, Google continues to block Microsoft from offering its customers proper access to YouTube. This is an important issue because consumers value YouTube access on their phone," said Microsoft attorney Dave Heiner in a blog post.

"Google often says that the antitrust offenses with which it has been charged cause no harm to consumers. Google is wrong about that. In this instance, for example, Google's refusal deprives consumers who use competing platforms of a comparable experience in accessing content that is generally available on the Web."

The comments marked the latest flare-up between the two tech titans and came as US and EU antitrust watchdogs were seeking to conclude probes into Google's conduct. Some reports said US investigators were preparing to settle for a voluntary agreement from Google without court enforcement.

Google, which owns YouTube, said Microsoft was distorting the facts on mobile phone access.

"Contrary to Microsoft's claims, it's easy for consumers to view YouTube videos on Windows phones," a Google spokesperson said in response to an AFP query.

"Windows phone users can access all the features of YouTube... In fact, we've worked with Microsoft for several years to help build a great YouTube experience on Windows phones."

Microsoft said it has raised its concerns both with the European Commission and the US Federal Trade Commission, which are investigation potential abuses of market dominance by Google.

"You might think that Google would be on its best behavior given it's under the bright lights of regulatory scrutiny on two continents," Heiner said.

"However, as we enter 2013, that is not the case... Hopefully, Google will wake up to a New Year with a resolution to change its ways and start to conform with the antitrust laws. If not, then 2013 hopefully will be the year when antitrust enforcers display the resolve that Google continues to lack."