General Keith Alexander, head of the US National Security Agency, on Tuesday took onlookers at a Congress hearing by surprise when he dismissed allegations that his agency had swept up data on millions of phone calls in Europe as "completely false".
Instead, he turned the tables on countries such as France, Germany and Spain - which have reacted with fierce anger to the spying allegations - saying that in many cases European spy agencies had handed phone call records over to them.
"The NSA director's denials don't seem likely," government spokeswoman Najat Vallaud-Belkacem said after a cabinet meeting.
She pointed to a pledge made last week by French President Francois Hollande and German Chancellor Angela Merkel, whose own phone was reportedly tapped, to reach an understanding with the United States on the conduct of intelligence gathering among allies.
"We must shine the light on the practices of the past and make sure that things work out for the best in the future... We cannot let doubt set in between partners," she added.
The allegations of US spying are based on information leaked by former US security contractor Edward Snowden and were published in European newspapers such as France's Le Monde and Germany's Der Spiegel.
They have rocked US President Barack Obama's administration, which claims to have repaired ties with key allies that frayed under former president George W. Bush.
But the outrage in Europe has been met with suspicion by some prominent US politicians, who say everyone spies on everyone at a time of anti-terror priorities.
Alexander and the Director of National Intelligence James Clapper on Tuesday said the reports that triggered such fury were based on a misunderstanding of the information passed by Snowden.
France's foreign ministry, meanwhile, said on Wednesday it was specifically concerned about the "nature and scale of US wiretapping on our territory".
"Where our intelligence agencies' surveillance activities are concerned, they are strictly framed by the law," spokesman Romain Nadal said.