The right to search laptop data will be limited under a new bill introduced to the US Senate today.

Three Democratic senators introduced a bill to ensure that the existing rules for the Department of Homeland Security are altered to protect data from random searches.

"Most Americans would be shocked to learn that, on their return to the US from abroad, the government could demand the password to their laptop, hold it for as long as it wants, pore over their documents, emails and photographs, and examine which websites they visited, all without any suggestion of wrongdoing," said Senator Russ Feingold.

"Focusing our limited law enforcement resources on law-abiding Americans who present no basis for suspicion does not make us any safer and is a gross violation of privacy.

"This bill will bring the government's practices at the border back in line with the reasonable expectations of law-abiding Americans."

Some European and Far Eastern businesses are so concerned by current laws that staff sent to the US are issued with data-free laptops in case company intellectual property is exposed.

As the law stands Department of Homeland Security staff can impound laptops and media devices indefinitely with no proof of wrongdoing.