Internt search giant Google has sued the US Department of the Interior alleging that the federal agency favoured rival Microsoft while considering bids for e-mail and collaboration software for its 88,000 employees.

In the suit filed in the US Court of Federal Claims, Google alleges that the US agency's request was written to "exclude Google's online services, Google Apps, by stating the system had to include the Microsoft Business Productivity Online Suite," the Wall Street Journal reported.

The Interior Department's decision to only consider Microsoft's standard is "unduly restrictive of competition," Google said in its complaint.

The Interior Department, which includes the National Park Service and Bureau of Indian Affairs, is looking for a web-based email and collaboration platform to replace 13 systems currently used by its 88,000 staffers.

The contract is estimated to be worth USD 59 million over five years.

"A fair and open process could save US taxpayers tens of millions of dollars and result in better services," the Journal quoted a Google spokesman as saying.

"We are asking the Department of Interior to allow for a true competition when selecting its technology providers.

"Google's lawsuit aims to block the Interior Department from proceeding with requests for bids on the contract without first conducting a competitive procurement process.

The Journal said according to the complaint, Interior officials told Google they were committed to an open competition for the contract even though the department had "standardised" on Microsoft technology.

Expressing concerns about whether Google could comply with the agency's security needs, the Interior Department concluded that Microsoft was the only vendor that met all of the department's requirements, the lawsuit added.