The US government allegedly continues to engage in mass surveillance on EU citizens despite assurances under a new data-sharing pact with the EU.

Edward Snowden, a former US national security agency intelligence contractor, told an audience in Brussels on Wednesday (7 September) that US government claims surveillance has been narrowed under the new EU-US Privacy Shield data sharing agreement is false.

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"It's categorically untrue," he said via video-link from Russia, where he has been granted asylum, at an event organised by German Green MEP Jan Philipp Albrecht.

"Governments don't like to hold themselves out as direct liars, saying something that is attributable and falsifiable," said Snowden.

The whistleblower, whose documents in 2013 revealed a US-led global digital dragnet, said that the Americans are instead twisting language in an effort to convince EU policy and lawmakers of falsehoods.

"They are denying they do mass surveillance, they are saying what we do do is bulk collection, which is in their world something entirely different, but in reality, in our world, it is mass surveillance," said Snowden.

Privacy Shield replaced the 15-year old Safe Harbour pact, which was declared invalid by the European Court of Justice last October over broader concerns linked to US mass surveillance programmes disclosed by Snowden.

Shield, for its part, is supposed to ensure the privacy rights of EU citizens whenever their data is used and then transferred to the US by companies like Google and Microsoft.

Penned between the European Commission and the US Department of Commerce, the transatlantic trade of EU data is said to have been worth over €200 billion annually under the old Safe Harbour scheme.

Snowden is not alone in casting doubts on the latest agreement. Top EU data protection authorities are also wary.

The EU's main regulatory body on privacy, the Article 29 Data Protection Working Party, earlier this year said US commitments not to carry mass surveillance under the pact were not good enough.

"The possibility that is left in the Shield and its annexes for bulk collection, which if massive and indiscriminate, is not acceptable," working party chair Isabelle Falque-Pierrotin told reporters in April.

The EU commission, for its part, says they have since received better assurances from the US following Falque-Pierrotin's April criticisms prior to Shield's operational launch at the start of August.

Those assurances centre around signed letters from top US authorities and includes a US-based ombudsperson to help steer compliance.

Some 200 US firms have since signed up to the self-certifying agreement, but many remain concerned the agreement may meet the same fate as Safe Harbour.

A survey of some 600 privacy professionals in the US and EU found that only 34 percent of companies intend to use the Privacy Shield framework.

Conducted by the International Association of Privacy Professionals and the consulting firm EY, the findings, published in late August, revealed that the vast majority will instead rely on other methods to transfer the data.

But those other transfer methods, known as standard contractual clauses, are also on shaky legal grounds and likely to be challenged by the European Court of Justice.

"Companies could be left without a viable legal channel for transferring data across the Atlantic, even as hundreds of billions of dollars in trade hang in the balance," said the report.