Google plans on selling more than $4bn of company stock only one year after the company's initial public flotation.

The search engine plans to use the proceeds of the flotation for working capital or possible future acquisitions, Google said in a filing with the Securities and Exchange Commission. The company stressed that it currently didn't have large acquisitions in the pipeline.

Google raised $1.7bn in its initial public offering last year. Since then shares in the company increased their value by 235 per cent to its current level of $280.

Since the IPO, Google has kept showing strong revenue growth and further expanded its business with local search and mapping applications.

In the regulatory filing, however, Google cautioned that it wouldn't be able to maintain its current growth rate.

"We expect that our revenue growth rate will decline over time and anticipate that there will be downward pressure on our operating margin." The company cited both increasing competition and the maturing of Google as a company as reasons for the levelling off.