Internet search giant Google on Wednesday said it will cut 300 of DoubleClick’s 1,200 employees, the online advertising company it purchased in March for $3.2 billion.

The layoffs, the largest in Google's history, come only three weeks after DoubleClick’s proposed purchase was approved by the European Commission, which put an end to eleven months of acquisition litigation.

“Since our acquisition of DoubleClick closed March 11, we have been working to match and align DoubleClick employees in the U.S. with our organizational plan for the business. As with many mergers, this review has resulted in a reduction in headcount at the acquired company,” the company said in a statement.

About a quarter of the advertising company’s employees will exit Wednesday, while others will be placed in transitional positions until both companies are fully merged, Google said in the statement.

DoubleClick’s remaining 300 overseas employees could see some layoffs in the future as well, Google’s statement said.

The cuts represent a small fraction of the Mountain View, California, company that counted over 16,800 employees worldwide at the end of 2007.

Google’s purchase of DoubleClick, the highest-priced acquisition in the search leader’s history, is intended to boost its revenue through ads that include pictures and video.

“With DoubleClick, Google now has the leading display ad platform, which will enable us to rapidly bring to market advances in technology,” Google CEO Eric Schmidt said in a March statement after the announcement of the acquisition.