Mumbai: Microsoft has been deploying lobbyists to oppose Google''s proposed purchase of DoubleClick, according to a recent public disclosure filing with the US Senate.

The world''s largest software maker sees internet search giant Google''s planned acquisition of DoubleClick as a "serious competitive issue" in the online-ad space.

The US Federal Trade Commission is currently looking into whether Google Inc.''s $3.1 billion buyout of online advertising company DoubleClick Inc passes antitrust muster.

Microsoft Corporation has hired Patton Boggs LLP to lobby the federal government on the acquisition, according to the filing.

Patton Boggs has employed lobbyists Thomas Boggs and Kathleen Ireland, along with Antitrust Modernisation Commission vice chairman and former Clinton White House attorney Jonathan Yarowsky on the job, the filing said.

The lobbysts'' charge, the filing said, is "competitive issues surrounding Google-DoubleClick merger."

Google, meanwhile, has repeatedly said it''s confident that the acquisition will benefit consumers and that the threat from its rival can be contained.

Google said it had also picked up four new lobbyists, including a former high-ranking department of justice antitrust lawyer, to help make the case for its DoubleClick acquisition.

Microsoft, meanwhile, sealed its own acquisition - a $6 billion takeover of aQuantive - last week. Antitrust authorities have already cleard that deal.