A US privacy group is appealing against the legal protection of telecom companies that participated in a wiretapping program during the presidency of George W. Bush.

The Electronic Frontier Foundation (EFF) is appealing, on behalf of several plaintiffs, a June federal court decision that upheld legislation that protects the companies, who acted without court authorization, from being prosecuted.

The 2008 law was approved by Congress at the urging of the Bush administration, which sought help from the companies to wiretap terror suspects under a program established in the wake of the September 11, 2001 attacks.

EFF argues that the legislation is "unconstitutional" because it grants "the attorney general the unconstrained power to decide whether to nullify existing federal and state law governing these actions."

The Bush administration program was revealed in December 2005 and provoked outrage because it circumvented a legal system set up to certify whether the government could carry out surveillance inside the United States.

The program was believed to primarily target non-Americans, but had the potential to include American citizens too.

EFF, a privacy group that focuses on civil rights on the Internet, is working with the American Civil Liberties Union on behalf of 46 plaintiffs to challenge the legislation.