Frontex's former boss and some of its staff covered up the pushbacks and lied to MEPs about it, a leaked report by the European Anti-Fraud Office (Olaf) states.
The former head of the European Union's external border surveillance agency Frontex was aware of the illegal deportations of migrants by Greece and even co-financed some of the returns, according to a damning report published on Thursday by Der Spiegel.
Frontex was aware very early on of these illegal and sometimes brutal returns of asylum seekers to Turkey, according to the confidential report by the European Anti-Fraud Office (Olaf), a leaked copy of which was also consulted by Le Monde newspaper and the Lighthouse Reports investigative website.
"Instead of preventing these pushbacks, former boss Fabrice Leggeri and his staff covered them up. They lied to the European Parliament and hid the fact that the agency supported some pushbacks with European taxpayers' money," the German magazine summarised.
The report reveals many details including how on 5 August 2020, the Greek coastguard towed a dinghy with 30 migrants on board not to Greece but to Turkey. A Frontex plane on patrol filmed the scene.
Instead of approaching the Greek authorities over the issue, Frontex stopped patrolling planes over the Aegean Sea on the grounds that it needed them elsewhere.
Investigators cite testimony from Frontex staff implicating Leggeri for turning a blind eye to these illegal acts and they found a written note referring to the withdrawal of surveillance planes "so as not to be a witness".
Contacted by Euronews, OLAF said that it "is not in a position to comment."
"OLAF's final reports are subject to strict rules of confidentiality and are in principle not made public by OLAF in order to protect the legitimate rights of the persons concerned, ensure the confidentiality of OLAF investigations and of possible follow-up in administrative proceedings, as well as for the protection of personal data," its press office added.
'We have the right to protect our borders'
During an official visit to Athens, German Foreign Minister Annalena Baerbock said we now know "thanks to the report on Frontex and the publication today by the anti-corruption authority (Olaf) there have been several cases (of illegal pushbacks)".
"Even if I obviously cannot verify in detail what happened in each individual case...there have been pushbacks that are incompatible with European law", the minister said during a visit to Frontex offices in Athens.
She stressed that "measures have been taken immediately (...), we have all talked about it today, to have more human rights observers on the spot," she added.
Olaf also reports that at least six Greek boats, co-financed by Frontex, were involved in more than a dozen pushbacks between April and December 2020, which the former director has always denied.
Greece has always denied any illegal pushbacks at its borders. Migration Minister Notis Mitarachi said on Thursday he had only read "the summary" of the Olaf report, which he stated "does not directly blame Greece".
"We have the right to protect our borders," he told the media.
Asked about the publication, a European Commission spokeswoman stressed that "a series of measures" had already been put in place to address the governance of the agency, which has been headed by Latvian Aija Kalnaja since early July.
"In terms of work on the ground with the Greek authorities, there is progress on the ground," added Commission spokeswoman Anitta Hipper, pointing also to "a new legislative proposal to ensure a robust monitoring system" for the treatment of asylum seekers in Greece.
During Leggeri's seven years at the helm of Frontex, the agency's staff was bolstered and should reach 10,000 coastguards and border guards by 2027.