The American Civil Liberties Union has filed a lawsuit over the seizure of laptops by border police without reason.

The court action is designed to obtain records of searches performed by the US Customs and Border Protection (CBP) of laptops and written materials from travellers entering the US.

The CBP currently conducts such searches, including taking images of hard drives, on anyone, rather than on people about whom they have reasonable suspicion.

"Travelling with a laptop should not mean that the government gets a free pass to rifle through your personal papers," said Catherine Crump, staff attorney with the ACLU First Amendment Working Group.

"This sort of broad and invasive search is exactly what the Fourth Amendment protections against unreasonable searches are designed to prevent."

The increase in such searches is causing headaches for companies. Many now issue travel laptops which contain no commercially sensitive information, and set up a File Transfer Protocol site for staff to download necessary data once through border security.

The ACLU originally requested the data in June, and began legal proceedings after gaining no response.

"Under CBP policy, innumerable international travellers have had their most personal information searched by government officials and retained by the government indefinitely," said Larry Schwartztol, staff attorney with the ACLU National Security Project.

"The disclosure of these records is necessary to better understand the extent to which US border and customs officials may be violating the Constitution."