Google was on the defensive on Capitol Hill on Thursday, fending off allegations from its chief rival, Microsoft, that its takeover of DoubleClick had grave antitrust and privacy implications for consumers.

David Drummond, chief legal officer at Google, defended the giant search company’s proposed deal with DoubleClick, the online advertising group it is acquiring for $3.1bn, by claiming the takeover would help the “relatively young” online advertising business grow and develop. He also promised that Google was “exploring” ways to create more transparency in its privacy practices and policies.