The Electronic Frontier Foundation (EFF) is making one more attempt to squash the controversial FISA Amendments Act.

The group has filed suit to challenge the constitutionality of the legislation, which shields US telecoms firms from lawsuits related to any cooperation with previous surveillance activities carried out by the National Security Agency.

Immunity had been a contentious point for backers and detractors of the FISA Act. Civil rights groups had long sought to block the passage of the bill until the sections providing immunity were removed.

US Congress eventually reached a compromise in which immunity could be granted if the NSA confirms to the judge that the surveillance was legal, authorised by the president, or simply did not happen.

The bill was then passed and signed into law by the government, despite continued appeals from rights groups such as the EFF.

"The immunity law puts the fox in charge of the hen house, letting the Attorney General decide whether or not telecoms [companies] like AT&T can be sued for participating in the government's illegal warrantless surveillance," said Kevin Bankston, an EFF senior staff attorney.

"The Attorney General should not be allowed to unconstitutionally play judge and jury in these cases, which affect the privacy of millions of Americans."

Because the bill has been signed into law, it can now be overturned only by a court decision or future legislative action. The EFF is relying on the former in the hope of overturning the law.

The case is set to go to court on 2 December in San Francisco, after the forthcoming presidential election but before the new administration takes office.