Software giant Microsoft is reportedly urging regulators to look into Google’s plan to buy DoubleClick, an online advertising company.

Microsoft contends that the $3.1 billion deal, announced on Friday, would hurt competition in the fast-growing market for advertising on the Web and raises questions about how much personal information would be collected by Google, already a dominant player in online advertising.

Bradford L. Smith, Microsoft’s general counsel, said in an interview yesterday that Google’s purchase of DoubleClick would combine the two largest online advertising distributors and thus “substantially reduce competition in the advertising market on the Web.”