Mauro Ferrari said he had lost faith in the system after he failed to set up a special programme to fight coronavirus.

But the research council said later his resignation followed a written, unanimous vote of no confidence.

It said it regretted Prof Ferrari's comments.

"Since his appointment, Professor Ferrari displayed a lack of engagement with the ERC, failing to participate in many important meetings, spending extensive time in the USA and failing to defend the ERC's programme and mission when representing the ERC," it said in a statement.

The EU's executive insisted it had the most comprehensive measures to combat the virus.

One MEP had earlier been quoted accusing Prof Ferrari of taking a "window-dressing public relations stand".

Who is Mauro Ferrari?

Mauro Ferrari is an Italian-American scientist known as a pioneer in the field of nanomedicine with decades of work in the US. When he took up the role as head of the European Research Council he stressed his commitment to serving society.

In a statement to the Financial Times and Corriere della Sera in Italy, he spoke of his commitment to the "idealistic dream of a United Europe... crushed by a very different reality".

As the tragedy of the pandemic became clear Prof Ferrari says he pushed for a special programme directed at combating Covid-19, with the world's best scientists having the resources to fight it with new drugs, vaccines, diagnostic tools and behavioural approaches based on sciences "to replace the oft-improvised intuitions of political leaders".

His proposals were rejected unanimously, he said, by the council's governing body because the ERC funded "bottom-up" research proposed by scientists themselves and did not see the beneficial impact on society as a justification for funding.

Prof Ferrari describes how he then worked directly with European Commission President Ursula von der Leyen and developed a plan which she contributed to.

However, he complains his direct involvement with Mrs von der Leyen "created an internal political thunderstorm" and once it went to the different parts of the Commission he believes it "disintegrated upon impact".

There are many questions surrounding the real reasons behind the resignation of Mauro Ferrari.

Yes, his stinging accusations about EU institutions weighed down by bureaucracy and internal politics ring true, but he will have known that before he agreed to become the bloc's chief scientist.

He will have also known that EU countries have always fought to keep sovereignty over national health services, so it is odd that he singled the lack of public health co-ordination across the EU as another reason for his departure.

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Prof Ferrari said he had worked directly with Ursula von der Leyen

In fact, high-level insiders in the European Research agency tell me Mr Ferrari's resignation was not voluntary. He was asked to leave, they say.

They say he was absent for half of the three months he was supposedly at the helm of the ERC, spending time instead in the US, where he has an affiliate professorship at the University of Washington as well as private interests in the pharmaceutical industry. He is listed on the board of directors at US biotech company Arrowhead Pharmaceuticals.

Mauro Ferrari announced he was now returning to the US to fight Covid-19 on the front line.

The ERC is eager to point out that many of its top scientists have already done that. It says virologists, epidemiologists and others who were doing basic research for them have now joined Covid research teams in other European Commission programmes.

Professor Ferrari's personal ambitions clashed with the cumbersome structures of the EU, perhaps. A crying shame on all sides when all hands are needed on deck in Europe, the US and globally to help protect the general public from coronavirus.

The research council detailed several of those points in its statement, saying:

• Prof Ferrari had failed to take part in important meetings and spent extensive time in the US
• he had made several personal initiatives within the Commission, without consulting or tapping into the ERC's collective knowledge
• he had been involved in multiple external enterprises, some academic and some commercial, which "appeared on several occasions to take precedence over his commitment to ERC"
• his workload proved to be incompatible with his mandate.

Speaking to the BBC's Newshour programme on Wednesday, Prof Ferrari said his departure was caused by a "very significant divergence of opinion" about the strategy needed for the current crisis. He also denied his other work commitments hindered his ability to fulfil the role.

The EU has often struggled to reach a consensus on tackling the Covid-19 outbreak. Finance ministers suspended talks early on Wednesday on how to help southern eurozone countries worst affected by the pandemic. The talks were due to resume on Thursday.

After Prof Ferrari's resignation, German MEP Christian Ehler told the Science Business website that Prof Ferrari's proposals contradicted the legal basis of the ERC and were a "window-dressing public relations stand on the coronavirus crisis".

One of the conditions for an ERC grant is that scientists apply for funding on a "bottom-up" basis for research either in a public or private research organisation.

A Commission spokesman said more 50 ERC projects had been involved in fighting the Covid-19 pandemic and 18 research and development proposals had been selected.- across a variety of scientific fields from virology to social behaviour.

Prof Ferrari said it was time for him to return to "the frontlines of the fight against Covid-19, with real resources and responsibilities, away from offices in Brussels, where my political skills are clearly inadequate".

The Commission said it was grateful for Prof Ferrari's "strong personal investment" and wished him well for the future.