FRONTEX, the European Border and Coastguard Agency, is “attempting to sue its critics into silence,” human rights activists warned today.

Transparency campaigners Luisa Izuzquiza and Arne Semsrott of the German organisation FragDenStaat (Ask The Country) filed a freedom of information request to Frontex last year asking the agency what types of boats it has in the Mediterranean.

Ms Izuzquiza and Mr Semsrott eventually took Frontex to court after it continuously refused to provide them with the information.

It was the first time a civil society organisation took such action against the border agency.

However the European Court ruled that Frontex did not have to disclose information regarding its border operations.

Then in January Frontex sent a letter to Ms Izuzquiza and Mr Semsrott’s legal representatives demanding €23,700 (£19,942) in legal fees.

The activists launched a petition yesterday demanding Frontex withdraw the bill.

“Frontex is now more powerful than ever,” the petition says.

“Its officials are allowed to use weapons at the border, and they have a billion-euro budget.

“The EU doesn’t care about the money. It wants to silence its critics. Support us! Not with money, but with your signature.”

If Frontex succeeds, FragDenStaat warns, “only businesses and the rich will be able to afford to take legal action against EU authorities — and critical civil society will be left out.

“Even now, actions for information against the European Union are particularly expensive. If authorities start imposing five-figure legal fees, lawsuits will become unaffordable.”