A couple whose Navy SEAL son was killed in Afghanistan have joined a class-action lawsuit against the U.S. government over the National Security Agency’s collection of Verizon phone records.

Charles and Mary Anne Strange joined the suit, which seeks billions in damages, after it was filed in federal court in D.C. on Sunday, accusing Obama’s administration of breaching the privacy of millions of Americans.

The couple, from Philadelphia, lost their 25-year-old son Michael in a helicopter crash on August 6, 2011 while he served in Afghanistan.

Mr Strange told CBS: ‘Somebody has to be held accountable for my son’s death. Thirty brave Americans, the biggest loss in the Afghan war.

‘And that’s when I started asking questions, that’s when my phone got tapped.’

The grieving father, from Torresdale, said he heard strange tapping noises during calls and received text messages from unknown numbers in the months after his son died.