The US Justice Department has recently ordered to run investigations over Google’s online advertising system, which could severely cost the technology giant $500m (£304m) as there are reports that Google's lucrative advertising system unfairly treats some unnamed advertisers.

A similar probe is being faced by Google by the European commission also because of its multibillion dollar business model, which easily comes under increased regulatory scrutiny around the world.

On Tuesday, Google sent its quarterly report to the US Securities and Exchange Commission, in which it highlighted about the potential $500m cost. Also, it was mentioned in the report that Google's advertising network that releases short text ads alongside relevant searches has accounted sales worth $8.3bn in the first quarter of this year to the company.

Moreover, an 18% rise in profit, leading figures to $2.3bn was marked by Google in the first three months of this year out of which $500m were set aside by the company earlier in the month, which reduced Google's net income to $1.8bn.

Google said in its filing: "In May 2011, in connection with a potential resolution of an investigation by the United States department of justice into the use of Google advertising by certain advertisers, we accrued $500m for the three month period ended March 31, 2011. Although we cannot predict the ultimate outcome of this matter, we believe it will not have a material adverse effect on our business, consolidated financial position, results of operations, or cash flows."