UPDATE 5-France, Germany blast Facebook's Libra, back public cryptocurrency

* ECB says work to accelerate on bankless digital cash

* France, Germany say Libra poses risk to EU states' sovereignty

* EU has no specific regulation for virtual currencies

* In EU's legal limbo, Malta developing its own rules (Adds comment by Libra Association, paragraphs 8-9)

By Francesco Guarascio

HELSINKI, Sept 13 (Reuters) - France and Germany said on Friday that Facebook Inc's Libra currency posed risks to the financial sector that could block its authorisation in Europe, and backed the development of an alternative public cryptocurrency.

The criticism came as the European Central Bank said it was working on a long-term plan to launch a public digital currency that could make projects such as Libra redundant.

Virtual currencies pose risks to consumers, financial stability and even "the monetary sovereignty" of European states, France's finance minister, Bruno Le Maire, and his German counterpart, Olaf Scholz, said in a joint statement issued at a meeting of euro zone finance ministers in Helsinki.

"France and Germany consider that the Libra project, as set out in Facebook's blueprint, fails to convince that those risks will be properly addressed," they said.

The 19-country euro zone bloc is united in pursuing a tough regulatory approach should Libra seek authorisations to operate in Europe, officials said at the meeting.

It is also considering a common set of rules for virtual currencies, which are currently largely unregulated.

The currency union has worked in past years on several plans to make digital payments cheaper and faster, but none of them has properly taken off so far.

The Libra Association, a 28-member organisation Facebook is setting up in Switzerland to manage the currency, said it welcomed the feedback.

Members "are committed to working with regulatory authorities to achieve a safe, transparent and consumer-focused implementation of the Libra project," Dante Disparte, the group's head of policy and communications, said in a statement.

WAKE-UP CALL

Plans unveiled in June by U.S. social media giant Facebook to launch its own digital currency, Libra, for payments among its hundreds of millions of users in Europe and around the world have triggered a rethink.

Libra was "a wake-up call", European Central Bank (ECB) board member Benoit Coeure told a news conference in Helsinki after a meeting of euro zone finance ministers.

He said Libra had revived efforts to widen the uptake of an ECB-backed project for real-time payments in the euro zone, known as TIPS. The project, launched last year, has been met with caution by banks.